Publications (18)62.81 Total impact
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Article: Long-term running alleviates some behavioral and molecular abnormalities in Down syndrome mouse model Ts65Dn.
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ABSTRACT: Running may affect the mood, behavior and neurochemistry of running animals. In the present study, we investigated whether voluntary daily running, sustained over several months, might improve cognition and motor function and modify the brain levels of selected proteins (SOD1, DYRK1A, MAP2, APP and synaptophysin) in Ts65Dn mice, a mouse model for Down syndrome (DS). Ts65Dn and age-matched wild-type mice, all females, had free access to a running wheel either from the time of weaning (post-weaning cohort) or from around 7 months of age (adult cohort). Sedentary female mice were housed in similar cages, without running wheels. Behavioral testing and evaluation of motor performance showed that running improved cognitive function and motor skills in Ts65Dn mice. However, while a dramatic improvement in the locomotor functions and learning of motor skills was observed in Ts65Dn mice from both post-weaning and adult cohorts, improved spatial memory was seen only in Ts65Dn mice that had free access to the wheel from weaning. The total levels of APP and MAP2ab were reduced and the levels of SOD1 were increased in the runners from the post-weaning cohort, while only the levels of MAP2ab and α-cleaved C-terminal fragments of APP were reduced in the adult group in comparison with sedentary trisomic mice. Hence, our study demonstrates that Ts65Dn females benefit from sustained voluntary physical exercise, more prominently if running starts early in life, providing further support to the idea that a properly designed physical exercise program could be a valuable adjuvant to future pharmacotherapy for DS.Experimental Neurology 11/2012; · 4.70 Impact Factor -
Article: Molecular chaperone alphaB-crystallin is expressed in the human fetal telencephalon at midgestation by a subset of progenitor cells.
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ABSTRACT: Alphab-crystallin (CRYAB) is a small heat shock protein with a chaperoning activity that is present in the postnatal healthy human brain in oligodendrocytes and in a few astrocytes. The involvement of CRYAB in cell differentiation, proliferation, signaling, cytoskeletal assembly, and apoptosis in various model systems has suggested that it might also play a role in the developing human brain. We analyzed the distribution and the levels of this molecular chaperone in healthy and polygenetically compromised (Down syndrome [DS]) human telencephalon at midgestation. We demonstrate that CRYAB is expressed in a temporospatial pattern by numerous radial glial cells and some early oligodendrocyte progenitors, including dividing cells, as well as a few astroglial cells in both healthy and DS fetal brains. We also found abundant phosphorylation of CRYAB at Ser-59, which mediates its antiapoptotic and cytoskeletal functions. There was only marginal phosphorylation at Ser-45.In contrast to our earlier study in young DS subjects, upregulation of phosphorylated CRYAB occurred rarely in DS fetuses. The distribution, the timing of appearance, and the results of colocalization studies suggest that CRYAB assists in the biological processes associated with developmental remodeling/differentiation and proliferation of select subpopulations of progenitor cells in human fetal brain at midgestation.Journal of Neuropathology and Experimental Neurology 07/2010; 69(7):745-59. · 4.26 Impact Factor -
Article: Functional consequences and rescue potential of pathogenic missense mutations in tripeptidyl peptidase I.
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ABSTRACT: There are 35 missense mutations among 68 different mutations in the TPP1 gene, which encodes tripeptidyl peptidase I (TPPI), a lysosomal aminopeptidase associated with classic late-infantile neuronal ceroid lipofuscinosis (CLN2 disease). To elucidate the molecular mechanisms underlying TPPI deficiency in patients carrying missense mutations and to test the amenability of mutant proteins to chemical chaperones and permissive temperature treatment, we introduced individually 14 disease-associated missense mutations into human TPP1 cDNA and analyzed the cell biology of these TPPI variants expressed in Chinese hamster ovary cells. Most TPPI variants displayed obstructed transport to the lysosomes, prolonged half-life of the proenzyme, and residual or no enzymatic activity, indicating folding abnormalities. Protein misfolding was produced by mutations located in both the prosegment (p.Gly77Arg) and throughout the length of the mature enzyme. However, the routes of removal of misfolded proteins by the cells varied, ranging from their efficient degradation by the ubiquitin/proteasome system to abundant secretion. Two TPPI variants demonstrated enhanced processing in response to folding improvement treatment, and the activity of one of them, p.Arg447His, showed a fivefold increase under permissive temperature conditions, which suggests that folding improvement strategies may ameliorate the function of some misfolding TPPI mutant proteins.Human Mutation 03/2010; 31(6):710-21. · 5.69 Impact Factor -
Article: A critical tryptophan and Ca2+ in activation and catalysis of TPPI, the enzyme deficient in classic late-infantile neuronal ceroid lipofuscinosis.
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ABSTRACT: Tripeptidyl aminopeptidase I (TPPI) is a crucial lysosomal enzyme that is deficient in the fatal neurodegenerative disorder called classic late-infantile neuronal ceroid lipofuscinosis (LINCL). It is involved in the catabolism of proteins in the lysosomes. Recent X-ray crystallographic studies have provided insights into the structural/functional aspects of TPPI catalysis, and indicated presence of an octahedrally coordinated Ca(2+). Purified precursor and mature TPPI were used to study inhibition by NBS and EDTA using biochemical and immunological approaches. Site-directed mutagenesis with confocal imaging technique identified a critical W residue in TPPI activity, and the processing of precursor into mature enzyme. NBS is a potent inhibitor of the purified TPPI. In mammalian TPPI, W542 is critical for tripeptidyl peptidase activity as well as autocatalysis. Transfection studies have indicated that mutants of the TPPI that harbor residues other than W at position 542 have delayed processing, and are retained in the ER rather than transported to lysosomes. EDTA inhibits the autocatalytic processing of the precursor TPPI. We propose that W542 and Ca(2+) are critical for maintaining the proper tertiary structure of the precursor proprotein as well as the mature TPPI. Additionally, Ca(2+) is necessary for the autocatalytic processing of the precursor protein into the mature TPPI. We have identified NBS as a potent TPPI inhibitor, which led in delineating a critical role for W542 residue. Studies with such compounds will prove valuable in identifying the critical residues in the TPPI catalysis and its structure-function analysis.PLoS ONE 01/2010; 5(8):e11929. · 4.09 Impact Factor -
Article: Upregulation of phosphorylated alphaB-crystallin in the brain of children and young adults with Down syndrome.
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ABSTRACT: Our previous proteomic studies disclosed upregulation of alphaB-crystallin, a small heat shock protein, in the brain tissue of Ts65Dn mice, a mouse model for Down syndrome (DS). To validate data obtained in model animals, we studied at present the levels and distribution of total alphaB-crystallin and its forms phosphorylated at Ser-45 and Ser-59 in the brain tissues of DS subjects and age-matched controls at 4 months to 23 years of age. On immunoblots from frontal cortex and white matter, alphaB-crystallin and its form phosphorylated at Ser-59 were detectable already in infants, whereas alphaB-crystallin phosphorylated at Ser-45 appeared in small amounts in older children. Although the levels of total alphaB-crystallin were modestly increased in DS subjects, the amounts of both phosphorylated forms were much higher (up to approximately 550%) in the group of older children and young adults with DS than in age-matched controls. Immunoreactivity to alphaB-crystallin occurred not only in a subset of oligodendrocytes and some subpial and perivascular astrocytes, which was reported earlier, but also in GFAP-positive astrocytes accumulating at the sites of ependymal injury as well as some GFAP/platelet-derived growth factor receptor alpha-positive cells in both DS and control brains, which is a novel observation. Given that the chaperone and anti-apoptotic activities of alphaB-crystallin are phosphorylation-dependent, we propose that enhanced phosphorylation of alphaB-crystallin in the brains of young DS subjects might reflect a cytoprotective mechanism mobilized in response to stress conditions induced or augmented by the effect of genes encoded by the triplicated chromosome 21.Brain research 04/2009; 1268:162-73. · 2.46 Impact Factor -
Article: Prosegment of tripeptidyl peptidase I is a potent, slow-binding inhibitor of its cognate enzyme.
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ABSTRACT: Tripeptidyl peptidase I (TPP I) is the first mammalian representative of a family of pepstatin-insensitive serine-carboxyl proteases, or sedolisins. The enzyme acts in lysosomes, where it sequentially removes tripeptides from the unmodified N terminus of small, unstructured polypeptides. Naturally occurring mutations in TPP I underlie a neurodegenerative disorder of childhood, classic late infantile neuronal ceroid lipofuscinosis (CLN2). Generation of mature TPP I is associated with removal of a long prosegment of 176 amino acid residues from the zymogen. Here we investigated the inhibitory properties of TPP I prosegment expressed and isolated from Escherichia coli toward its cognate protease. We show that the TPP I prosegment is a potent, slow-binding inhibitor of its parent enzyme, with an overall inhibition constant in the low nanomolar range. We also demonstrate the protective effect of the prosegment on alkaline pH-induced inactivation of the enzyme. Interestingly, the inhibitory properties of TPP I prosegment with the introduced classic late infantile neuronal ceroid lipofuscinosis disease-associated mutation, G77R, significantly differed from those revealed by wild-type prosegment in both the mechanism of interaction and the inhibitory rate. This is the first characterization of the inhibitory action of the sedolisin prosegment.Journal of Biological Chemistry 07/2008; 283(24):16497-504. · 4.77 Impact Factor -
Article: Increased levels of carbonic anhydrase II in the developing Down syndrome brain.
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ABSTRACT: By using a proteomic approach, we found increased levels of carbonic anhydrase II (CA II) in the brain of Ts65Dn mice, a mouse model for Down syndrome (DS). Further immunoblot analyses showed that the levels of CA II are increased not only in the brain of adult Ts65Dn mice but also in the brain of infants and young children with DS. Cellular localization of the enzyme in human brain, predominantly in the oligodendroglia and primitive vessels in fetal brain and in the oligodendroglia and some GABAergic neurons postnatally, was similar in DS subjects and controls. Given the role of CA II in regulation of electrolyte and water balance and pH homeostasis, up-regulation of CA II may reflect a compensatory mechanism mobilized in response to structural/functional abnormalities in the developing DS brain. However, this up-regulation may also have an unfavorable effect by increasing susceptibility to seizures of children with DS.Brain Research 02/2008; 1190:193-205. · 2.73 Impact Factor -
Article: Tripeptidyl-peptidase I in health and disease.
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ABSTRACT: The lysosomal lumen contains numerous acidic hydrolases involved in the degradation of carbohydrates, lipids, proteins, and nucleic acids, which are basic cell components that turn over continuously within the cell and/or are ingested from outside of the cell. Deficiency in almost any of these hydrolases causes accumulation of the undigested material in secondary lysosomes, which manifests itself as a form of lysosomal storage disorder (LSD). Mutations in tripeptidyl-peptidase I (TPP I) underlie the classic late-infantile form of neuronal ceroid lipofuscinoses (CLN2), the most common neurodegenerative disorders of childhood. TPP I is an aminopeptidase with minor endopeptidase activity and Ser475 serving as an active-site nucleophile. The enzyme is synthesized as a highly glycosylated precursor transported by mannose-6-phosphate receptors to lysosomes, where it undergoes proteolytic maturation. This review summarizes recent progress in understanding of TPP I biology and molecular pathology of the CLN2 disease process, including distribution of the enzyme, its biosynthesis, glycosylation, transport and activation, as well as catalytic mechanisms and their potential implications for pathogenesis and treatment of the underlying disease. Promising data from gene and stem cell therapy in laboratory animals raise hope that CLN2 will be the first neurodegenerative LSD for which causative treatment will become available for humans.Biological Chemistry 09/2006; 387(8):1091-9. · 2.96 Impact Factor -
Article: Carbonic anhydrase II in the developing and adult human brain.
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ABSTRACT: Carbonic anhydrase II (CA II) is one of 14 isozymes of carbonic anhydrases, zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide to bicarbonate. Mutations in CA II in humans lead to osteopetrosis with renal tubular acidosis and cerebral calcifications, a disorder often associated with mental retardation. Recently, new avenues in CA II research have opened as a result of discoveries that the enzyme increases bicarbonate and proton fluxes and may play an important role in brain tissue. In the human brain, CA II was localized to oligodendrocytes, myelin, and choroid plexus epithelium. Because this conclusion was based on a few fragmentary reports, we analyzed in more detail the expression of the enzyme in human telencephalon. By immunoblotting, we found a gradual increase in CA II levels from 17 weeks' gestation to childhood and adolescence. By immunohistochemistry, CA II was found to be present not only in oligodendrocytes and choroid plexus epithelium (declining with aging in both these locations), but also in a subset of neurons mostly with GABAergic phenotype, in a few astrocytes, and transiently during brain development in the endothelial cells of microvessels. The enzyme also occurred in oligodendrocyte processes in contact with myelinating axons, myelin sheaths, and axolemma, but was either absent or appeared in minute amounts in compact myelin. These findings suggest the possible involvement of CA II in a wide spectrum of biologic processes in the developing and adult human brain and may contribute to better understanding of the pathogenesis of cerebral calcifications and mental retardation caused by CA II deficiency.Journal of Neuropathology and Experimental Neurology 08/2006; 65(7):664-74. · 4.26 Impact Factor -
Article: Glycosaminoglycans modulate activation, activity, and stability of tripeptidyl-peptidase I in vitro and in vivo.
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ABSTRACT: Tripeptidyl-peptidase I (TPP I, CLN2 protein) is a lysosomal exopeptidase that sequentially removes tripeptides from the N termini of polypeptides and shows a minor endoprotease activity. Mutations in TPP I lead to classic late-infantile neuronal ceroid lipofuscinosis, a neurodegenerative lysosomal storage disease. TPP I proenzyme is converted in lysosomes into a mature enzyme with the assistance of another protease and is able to autoactivate in acidic pH in vitro via a unimolecular mechanism. Because autoactivation in vitro at the pH values reported for lysosomes generated inactive enzyme, we intended to determine whether physiologically relevant factors can modify this process to also make it plausible in vivo. Here, we report that high ionic strength and glycosaminoglycans (GAGs) increase yields (ionic strength) or yields and rates (GAGs) of activation, enhance degradation of liberated TPP I prosegment fragments, and switch effective autoactivation of TPP I proenzyme toward less acidic pH values (up to pH 6.0). Although ionic strength and GAGs also inhibited TPP I activity in vitro and in living cells, the degree of inhibition (from 20 to 60%) appears to be of rather limited functional significance. Importantly, binding to GAGs improved thermal stability of TPP I and protected the enzyme against alkaline pH-induced denaturation in vitro (t((1/2)) of mature enzyme at pH 7.4 increased by approximately 8-fold in the presence of heparin) and in vivo ( approximately 2-fold higher loss of TPP I in cells deficient in GAGs than in control cells after bafilomycin A1 treatment). These findings elucidate a potent physiologically relevant mechanism of TPP I regulation by GAGs and suggest that generation of the active enzyme via autoactivation can be accomplished not only in vitro but in vivo as well.Journal of Biological Chemistry 04/2005; 280(9):7550-61. · 4.77 Impact Factor -
Article: Ser475, Glu272, Asp276, Asp327, and Asp360 are involved in catalytic activity of human tripeptidyl-peptidase I.
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ABSTRACT: Tripeptidyl-peptidase I (TPP I) is a lysosomal aminopeptidase that sequentially removes tripeptides from small polypeptides and also shows a minor endoprotease activity. Mutations in TPP I are associated with a fatal lysosomal storage disorder--the classic late-infantile form of neuronal ceroid lipofuscinoses. In the present study, we analyzed the catalytic mechanism of the human enzyme by using a site-directed mutagenesis. We demonstrate that apart from previously identified Ser475 and Asp360, also Glu272, Asp276, and Asp327 are important for catalytic activity of the enzyme. Involvement of serine, glutamic acid, and aspartic acid in the catalytic reaction validates the idea, formulated on the basis of significant amino acid sequence homology and inhibition studies, that TPP I is the first mammalian representative of a growing family of serine-carboxyl peptidases.FEBS Letters 03/2005; 579(6):1383-8. · 3.54 Impact Factor -
Article: Maturation of human tripeptidyl-peptidase I in vitro.
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ABSTRACT: Tripeptidyl-peptidase I (TPP I, CLN2 protein) is a lysosomal aminopeptidase that cleaves off tripeptides from the free N termini of oligopeptides and also shows minor endopeptidase activity. TPP I is synthesized as a preproenzyme. Its proenzyme autoactivates under acidic conditions in vitro, resulting in a rapid conversion into the mature form. In this study, we examined the process of maturation in vitro of recombinant latent human TPP I purified to homogeneity from secretions of Chinese hamster ovary cells overexpressing TPP I cDNA. Autoprocessing of TPP I proenzyme was carried out at a wide pH range, from approximately 2.0 to 6.0, albeit with different efficiencies depending on the pH and the type of buffer. However, the acquisition of enzymatic activity in the same buffer took place in a narrower pH "window," usually in the range of 3.6-4.2. N-terminal sequencing revealed that mature, inactive enzyme generated during autoactivation at higher pH contained N-terminal extensions (starting at 6 and 14 amino acid residues upstream of the prosegment/mature enzyme junction), which could contribute to the lack of activity of TPP I generated in this manner. Autoprocessing was not associated with any major changes of the secondary structure of the proenzyme, as revealed by CD spectroscopy. Both the activation and proteolytic processing of the recombinant TPP I precursor were primarily concentration-independent. The addition of the mature enzyme did not accelerate the processing of the proenzyme. In addition, the maturation of the proenzyme was not affected by the presence of glycerol. Finally, the proenzyme with the active site mutated (S475L) was not processed in the presence of the wild-type enzyme. All of these findings indicate a primarily intramolecular (unimolecular) mechanism of TPP I activation and autoprocessing and suggest that in vivo mature enzyme does not significantly participate in its own generation from the precursor.Journal of Biological Chemistry 08/2004; 279(30):31058-67. · 4.77 Impact Factor -
Article: N-glycosylation is crucial for folding, trafficking, and stability of human tripeptidyl-peptidase I.
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ABSTRACT: Tripeptidyl-peptidase I (TPP I) is a lysosomal serine-carboxyl peptidase that sequentially removes tripeptides from polypeptides. Naturally occurring mutations in TPP I are associated with the classic late infantile neuronal ceroid lipofuscinosis. Human TPP I has five potential N-glycosylation sites at Asn residues 210, 222, 286, 313, and 443. To analyze the role of N-glycosylation in the function of the enzyme, we obliterated each N- glycosylation consensus sequence by substituting Gln for Asn, either individually or in combinations, and expressed mutated cDNAs in Chinese hamster ovary and human embryonic kidney 293 cells. Here, we demonstrate that human TPP I in vivo utilizes all five N-glycosylation sites. Elimination of one of these sites, at Asn-286, dramatically affected the folding of the enzyme. However, in contrast to other misfolded proteins that are retained in the endoplasmic reticulum, only a fraction of misfolded TPP I mutant expressed in Chinese hamster ovary cells, but not in human embryonic kidney 293 cells, was arrested in the ER, whereas its major portion was secreted. Secreted proenzyme formed non-native, interchain disulfide bridges and displayed only residual TPP I activity upon acidification. A small portion of TPP I missing Asn-286-linked glycan reached the lysosome and was processed to an active species; however, it showed low thermal and pH stability. N-Glycans at Asn-210, Asn-222, Asn-313, and Asn-443 contributed slightly to the specific activity of the enzyme and its resistance to alkaline pH-induced inactivation. Phospholabeling experiments revealed that N-glycans at Asn-210 and Asn-286 of TPP I preferentially accept a phosphomannose marker. Thus, a dual role of oligosaccharide at Asn-286 in folding and lysosomal targeting could contribute to the unusual, but cell type-dependent, fate of misfolded TPP I conformer and represent the molecular basis of the disease process in subjects with naturally occurring missense mutation at Asn-286.Journal of Biological Chemistry 04/2004; 279(13):12827-39. · 4.77 Impact Factor -
Article: Biosynthesis, glycosylation, and enzymatic processing in vivo of human tripeptidyl-peptidase I.
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ABSTRACT: Human tripeptidyl-peptidase I (TPP I, CLN2 protein) is a lysosomal serine protease that removes tripeptides from the free N termini of small polypeptides and also shows a minor endoprotease activity. Due to various naturally occurring mutations, an inherited deficiency of TPP I activity causes a fatal lysosomal storage disorder, classic late infantile neuronal ceroid lipofuscinosis (CLN2). In the present study, we analyzed biosynthesis, glycosylation, transport, and proteolytic processing of this enzyme in stably transfected Chinese hamster ovary cells as well as maturation of the endocytosed proenzyme in CLN2 lymphoblasts, fibroblasts, and N2a cells. Human TPP I was initially identified as a single precursor polypeptide of approximately 68 kDa, which, within a few hours, was converted to the mature enzyme of approximately 48 kDa. Compounds affecting the pH of intracellular acidic compartments, those interfering with the intracellular vesicular transport as well as inhibition of the fusion between late endosomes and lysosomes by temperature block or 3-methyladenine, hampered the conversion of TPP I proenzyme into the mature form, suggesting that this process takes place in lysosomal compartments. Digestion of immunoprecipitated TPP I proenzyme with both N-glycosidase F and endoglycosidase H as well as treatment of the cells with tunicamycin reduced the molecular mass of TPP I proenzyme by approximately 10 kDa, which indicates that all five potential N-glycosylation sites in TPP I are utilized. Mature TPP I was found to be partially resistant to endo H treatment; thus, some of its N-linked oligosaccharides are of the complex/hybrid type. Analysis of the effect of various classes of protease inhibitors and mutation of the active site Ser(475) on human TPP I maturation in cultured cells demonstrated that although TPP I zymogen is capable of autoactivation in vitro, a serine protease that is sensitive to AEBSF participates in processing of the proenzyme to the mature, active form in vivo.Journal of Biological Chemistry 03/2003; 278(9):7135-45. · 4.77 Impact Factor -
Article: Distribution of Tripeptidyl Peptidase I in Human Tissues Under Normal and Pathological Conditions
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ABSTRACT: Tripeptidyl peptidase I (TPP I) is a lysosomal exopeptidase that cleaves tripeptides from the free N-termini of oligopeptides. Mutations in this enzyme are associated with the classic late-infantile form of neuronal ceroid lipofuscinosis (CLN2), an autosomal recessive disorder leading to severe brain damage. To gain more insight into CLN2 pathogenesis and the role of TPP I in human tissues in general, we analyzed the temporal and spatial distribution of TPP I in the brain and its localization in internal organs under normal and pathological conditions. We report that TPP I immunoreactivity appears in neurons late in gestation and increases gradually in the postnatal period, matching significantly the final differentiation and maturation of neural tissue. Endothelial cells, choroid plexus, microglial cells, and ependyma showed TPP I immunostaining distinctly earlier than neurons. Acquisition of the adult pattern of TPP I distribution in the brain at around the age of 2 years correlates with the onset of clinical signs in CLN2 subjects. In adults, TPP I was found in all types of cells in the brain and internal organs we studied, although the intensity of TPP I labeling varied among several types of cells and showed a noticeable predilection for cells and/or organs associated with peptide hormone and neuropeptide production. In addition, TPP I immunoreactivity was increased in aging brain, neurodegenerative and lysosomal storage disorders, and some differentiated neoplasms and was reduced in ischemic/anoxic areas and undifferentiated tumors. These findings suggest that TPP I is involved in general protein turnover and that its expression may be controlled by various regulatory mechanisms, which highlights the importance of this enzyme for normal function of cells and organs in humans.Journal of Neuropathology and Experimental Neurology 02/2001; 60(3):280–292. · 4.26 Impact Factor -
Article: Tripeptidyl-peptidase 1 in neuronal ceroid lipofuscinoses and other lysosomal storage disorders
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ABSTRACT: The classic late infantile form of neuronal ceroid lipofuscinosis (CLN2, cLINCL) is associated with mutations in the gene encoding tripeptidyl-peptidase I (TPP-I), a lysosomal aminopeptidase that cleaves off tripeptides from the free N-termini of oligopeptides. To date over 30 different mutations and 14 polymorphisms associated with CLN2 disease process have been identified. In the present study, we analysed the molecular basis of 15 different mutations of TPP-I by using immunocytochemistry, immunofluorescence, Western blotting, enzymatic assay and subcellular fractionation. In addition, we studied the expression of TPP-I in other lysosomal storage disorders such as CLN1, CLN3, muccopolysaccharidoses and GM1 and GM2 gangliosidoses. Our study shows that TPP-I is absent or appears in very small amounts not only in cLINCL subjects with mutations producing severely truncated protein, but also in individuals with missense point mutations, which correlates with loss of TPP-I activity. Of interest, small amounts of TPP-I were detected in lysosomal fraction from fibroblasts from cLINCL subject with protracted form. This observation suggests that the presence of small amounts of TPP-I in lysosomes is able to delay significantly CLN2 disease process. We also show that TPP-I immunoreactivity is increased in the brain tissue of CLN1 and CLN3 subjects, stronger in glial cells and macrophages than neurons. Less prominent increase of TPP-I staining was found in muccopolysaccharidoses and GM, and GM2 gangliosidoses. These data suggest that TPP-I participates in lysosomal turnover of proteins in pathological conditions associated with cell/tissue injury.European Journal of Paediatric Neurology. 5:73-79. -
Article: CLN3 Protein Regulates Lysosomal pH and Alters Intracellular Processing of Alzheimer's Amyloid-β Protein Precursor and Cathepsin D in Human Cells
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ABSTRACT: Maintenance of the appropriate pH in the intracellular vacuolar compartments is essential for normal cell function. Here, we report that CLN3 protein, which is associated with the juvenile form of neuronal ceroid lipofuscinosis (JNCL), participates in lysosomal pH homeostasis in human cells. We show that CLN3 protein increases lysosomal pH in cultured human embryonal kidney cells, whereas inhibition of CLN3 protein synthesis by antisense approach acidifies lysosomal compartments. These changes in lysosomal pH are sufficient to exert a significant biological effect and modify intracellular processing of amyloid-β protein precursor and cathepsin D, model proteins whose metabolism is influenced by the pH of acidic organelles. Mutant CLN3 protein (R334C) that is associated with the classical JNCL phenotype was devoid of biological activities of wild-type CLN3 protein. These data suggest that the pathogenesis of juvenile neuronal ceroid lipofuscinosis is associated with altered acidification of lysosomal compartments. Furthermore, our study indicates that CLN3 protein affects metabolism of proteins essential for cell functions, such as amyloid-β protein precursor, implicated in Alzheimer's disease pathogenesis.Molecular Genetics and Metabolism. -
Article: 2 Cellular pathology and pathogenic aspects of neuronal ceroid lipofuscinoses
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ABSTRACT: Lysosomal accumulation of autofluorescent, ceroid lipopigment material in various tissues and organs is a common feature of the neuronal ceroid lipofuscinoses (NCLs). However, recent clinicopathologic and genetic studies have evidenced that NCLs encompass a group of highly heterogeneous disorders. In five of the eight NCL variants distinguished at present, genes associated with the disease process have been isolated and characterized (CLN1, CLN2, CLN3, CLN5, CLN8). Only products of two of these genes, CLN1 and CLN2, have structural and functional properties of lysosomal enzymes. Nevertheless, according to the nature of the material accumulated in the lysosomes, NCLs in humans as well as natural animal models of these disorders can be divided into two major groups: those characterized by the prominent storage of saposins A and D, and those showing the predominance of subunit c of mitochondrial ATP synthase accumulation. Thus, taking into account the chemical character of the major component of the storage material, NCLs can be classified currently as preoteinoses. Of importance, although lysosomal storage material accumulates in NCL subjects in various organs, only brain tissue shows severe dysfunction and cell death, another common feature of the NCL disease process. However, the relation between the genetic defects associated with the NCL forms, the accumulation of storage material, and tissue damage is still unknown. This chapter introduces the reader to the complex pathogenesis of NCLs and summarizes our current knowledge of the potential consequences of the genetic defects of NCL-associated proteins on the biology of the cell.Advances in Genetics.
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2001–2012
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New York State Institute for Basic Research in Developmental Disabilities
New York City, NY, USA
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