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Dorothée Sturm,
Lorella Marselli,
Florian Ehehalt,
Daniela Richter,
Marius Distler,
Stephan Kersting,
Robert Grützmann,
Krister Bokvist,
Philippe Froguel,
Robin Liechti,
Anne Jörns,
Paolo Meda,
Gustavo Bruno Baretton,
Hans-Detlev Saeger,
Anke M Schulte,
Piero Marchetti, Michele Solimena
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ABSTRACT: Laser microdissection (LMD) is a technique that allows the recovery of selected cells and tissues from minute amounts of parenchyma (1,2). The dissected cells can be used for a variety of investigations, such as transcriptomic or proteomic studies, DNA assessment or chromosomal analysis (2,3). An especially challenging application of LMD is transcriptome analysis, which, due to the lability of RNA (4), can be particularly prominent when cells are dissected from tissues that are rich of RNases, such as the pancreas. A microdissection protocol that enables fast identification and collection of target cells is essential in this setting in order to shorten the tissue handling time and, consequently, to ensure RNA preservation. Here we describe a protocol for acquiring human pancreatic beta cells from surgical specimens to be used for transcriptomic studies (5). Small pieces of pancreas of about 0.5-1 cm(3) were cut from the healthy appearing margins of resected pancreas specimens, embedded in Tissue-Tek O.C.T. Compound, immediately frozen in chilled 2-Methylbutane, and stored at -80 °C until sectioning. Forty serial sections of 10 μm thickness were cut on a cryostat under a -20 °C setting, transferred individually to glass slides, dried inside the cryostat for 1-2 min, and stored at -80 °C. Immediately before the laser microdissection procedure, sections were fixed in ice cold, freshly prepared 70% ethanol for 30 sec, washed by 5-6 dips in ice cold DEPC-treated water, and dehydrated by two one-minute incubations in ice cold 100% ethanol followed by xylene (which is used for tissue dehydration) for 4 min; tissue sections were then air-dried afterwards for 3-5 min. Importantly, all steps, except the incubation in xylene, were performed using ice-cold reagents - a modification over a previously described protocol (6). utilization of ice cold reagents resulted in a pronounced increase of the intrinsic autofluorescence of beta cells, and facilitated their recognition. For microdissection, four sections were dehydrated each time: two were placed into a foil-wrapped 50 ml tube, to protect the tissue from moisture and bleaching; the remaining two were immediately microdissected. This procedure was performed using a PALM MicroBeam instrument (Zeiss) employing the Auto Laser Pressure Catapulting (AutoLPC) mode. The completion of beta cell/islet dissection from four cryosections required no longer than 40-60 min. Cells were collected into one AdhesiveCap and lysed with 10 μl lysis buffer. Each single RNA specimen for transcriptomic analysis was obtained by combining 10 cell microdissected samples, followed by RNA extraction using the Pico Pure RNA Isolation Kit (Arcturus). This protocol improves the intrinsic autofluorescence of human beta cells, thus facilitating their rapid and accurate recognition and collection. Further improvement of this procedure could enable the dissection of phenotypically different beta cells, with possible implications for better understanding the changes associated with type 2 diabetes.
Journal of Visualized Experiments 01/2013;
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ABSTRACT: Die Entwicklung eines Diabetes mellitus stellt eine häufige Komplikation von Erkrankungen des Pankreas dar. Wenngleich die
Therapie der Primärerkrankung im Vordergrund steht, ist die Behandlung des sekundären Diabetes häufig eine große Herausforderung
in der täglichen Praxis und hat entscheidende Bedeutung für die Lebensqualität der Betroffenen. Im vorliegenden Beitrag werden
die relevanten Krankheitsbilder der Bauchspeicheldrüse besprochen, die mit der Entwicklung eines Diabetes assoziiert sind
und entscheidende Therapiestrategien erläutert. Darüber hinaus soll die Bedeutung eines neu manifestierten Diabetes als richtungweisendes
Symptom für die Diagnose von Pankreaserkrankungen dargestellt werden.
The onset of diabetes mellitus is a common complication among patients with pancreatic disease. Although treatment of the
primary disease takes priority over secondary complications, diabetes often represents a challenge in daily practice and has
a major impact on the long-term prognosis and quality of life in those patients. This report provides information on the most
relevant clinical conditions of the pancreas associated with diabetes and describes therapeutic strategies. Furthermore, the
significance of new onset diabetes for early diagnosis of pancreatic disease is discussed.
Der Diabetologe 04/2012; · 0.25 Impact Factor
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Samantha M Bonner,
Susan L Pietropaolo,
Yong Fan,
Yigang Chang,
Praveen Sethupathy,
Michael P Morran,
Megan Beems,
Nick Giannoukakis,
Giuliana Trucco,
Michael O Palumbo, Michele Solimena,
Alberto Pugliese,
Constantin Polychronakos,
Massimo Trucco,
Massimo Pietropaolo
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ABSTRACT: ICA69 (islet cell autoantigen 69 kDa) is a protein implicated in type 1 diabetes mellitus in both the non-obese diabetic (NOD) mouse model and humans. ICA69 is encoded by the Ica1 gene on mouse chromosome 6 A1-A2. We previously reported reduced ICA69 expression in the thymus of NOD mice compared with thymus of several non-diabetic mouse strains. We propose that reduced thymic ICA69 expression could result from variations in transcriptional regulation of the gene and that polymorphisms within the Ica1 core promoter may partially determine this transcriptional variability. We characterized the functional promoter of Ica1 in NOD mice and compared it with the corresponding portions of Ica1 in non-diabetic C57BL/6 mice. Luciferase reporter constructs demonstrated that the NOD Ica1 promoter region exhibited markedly reduced luciferase expression in transiently transfected medullary thymus epithelial (mTEC(+)) and B-cell (M12)-derived cell lines. However, in a non-diabetic strain, C57BL/6, the Ica1 promoter region was transcriptionally active when transiently transfected into the same cell lines. We concomitantly identified five single nucleotide polymorphisms within the NOD Ica1 promoter. One of these single nucleotide polymorphisms increases the binding affinity for the transcription factor AIRE (autoimmune regulator), which is highly expressed in thymic epithelial cells, where it is known to play a key role regulating self-antigen expression. We conclude that polymorphisms within the NOD Ica1 core promoter may determine AIRE-mediated down-regulation of ICA69 expression in medullary thymic epithelial cells, thus providing a novel mechanistic explanation for the loss of immunologic tolerance to this self-antigen in autoimmunity.
Journal of Biological Chemistry 03/2012; 287(21):17882-93. · 4.77 Impact Factor
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ABSTRACT: The size composition of human islet preparations has been attributed to functional potency, islet survival and transplantation outcomes. In the early post-transplantation phase islets are supplied with oxygen by diffusion only and are at risk of critical hypoxia. The high rate of early islet graft dysfunction is in part attributed to this condition. It has been presumed that islets with smaller diameter, and therefore smaller diffusion distance, are superior to large islets regarding early survival rate and graft function. In this study we aimed to evaluate Complex Object Parametric Analysis and Sorting (COPAS) as a device for automated sorting of human islets. The use of COPAS was validated for accuracy and sensitivity using polystyrene beads of known diameters. Based on time of flight relative to particle isolated islets were then automatically sorted and analyzed for viability and function using handpicked islets as control. Our results suggest that COPAS enables the automated and accurate sorting of islets with no negative impact on their integrity and viability. Thus, COPAS is an adequate tool for size-specific analysis of pancreatic islets and may be considered as part of a platform for automated high-throughput screening of pancreatic islets.
Islets 09/2011; 3(5):267-70.
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ABSTRACT: Investigations into the pathogenesis of type 2 diabetes and islets of Langerhans malfunction (1) have been hampered by the limited availability of type 2 diabetic islets from organ donors(2). Here we share our protocol for isolating islets from human pancreatic tissue obtained from type 2 diabetic and non-diabetic patients who have undergone partial pancreatectomy due to different pancreatic diseases (benign or malignant pancreatic tumors, chronic pancreatitis, and common bile duct or duodenal tumors). All patients involved gave their consent to this study, which had also been approved by the local ethics committee. The surgical specimens were immediately delivered to the pathologist who selected soft and healthy appearing pancreatic tissue for islet isolation, retaining the damaged tissue for diagnostic purposes. We found that to isolate more than 1,000 islets, we had to begin with at least 2 g of pancreatic tissue. Also essential to our protocol was to visibly distend the tissue when injecting the enzyme-containing media and subsequently mince it to aid digestion by increasing the surface area. To extend the applicability of our protocol to include the occasional case in which a large amount (>15g) of human pancreatic tissue is available , we used a Ricordi chamber (50 ml) to digest the tissue. During digestion, we manually shook the Ricordi chamber(3) at an intensity that varied by specimen according to its level of tissue fibrosis. A discontinous Ficoll gradient was then used to separate the islets from acinar tissue. We noted that the tissue pellet should be small enough to be homogenously resuspended in Ficoll medium with a density of 1.125 g/ml. After isolation, we cultured the islets under stress free conditions (no shaking or rotation) with 5% CO(2;) at 37 °C for at least 48 h in order to facilitate their functional recovery. Widespread application of our protocol and its future improvement could enable the timely harvesting of large quantities of human islets from diabetic and clinically matched non-diabetic subjects, greatly advancing type 2 diabetes research.
Journal of Visualized Experiments 01/2011;
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ABSTRACT: Polypyrimidine-tract binding protein 1 (PTBP1) is an important cellular regulator of messenger RNAs influencing the alternative splicing profile of a cell as well as its mRNA stability, location and translation. In addition, it is diverted by some viruses to facilitate their replication. Here, we used a novel PTBP1 knockout mouse to analyse the tissue expression pattern of PTBP1 as well as the effect of its complete removal during development. We found evidence of strong PTBP1 expression in embryonic stem cells and throughout embryonic development, especially in the developing brain and spinal cord, the olfactory and auditory systems, the heart, the liver, the kidney, the brown fat and cartilage primordia. This widespread distribution points towards a role of PTBP1 during embryonic development. Homozygous offspring, identified by PCR and immunofluorescence, were able to implant but were arrested or retarded in growth. At day 7.5 of embryonic development (E7.5) the null mutants were about 5x smaller than the control littermates and the gap in body size widened with time. At mid-gestation, all homozygous embryos were resorbed/degraded. No homozygous mice were genotyped at E12 and the age of weaning. Embryos lacking PTBP1 did not display differentiation into the 3 germ layers and cavitation of the epiblast, which are hallmarks of gastrulation. In addition, homozygous mutants displayed malformed ectoplacental cones and yolk sacs, both early supportive structure of the embryo proper. We conclude that PTBP1 is not required for the earliest isovolumetric divisions and differentiation steps of the zygote up to the formation of the blastocyst. However, further post-implantation development requires PTBP1 and stalls in homozygous null animals with a phenotype of dramatically reduced size and aberration in embryonic and extra-embryonic structures.
PLoS ONE 01/2011; 6(2):e16992. · 4.09 Impact Factor
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ABSTRACT: ICA512 (or IA-2) is a transmembrane protein-tyrosine phosphatase located in secretory granules of neuroendocrine cells. Initially, it was identified as one of the main antigens of autoimmune diabetes. Later, it was found that during insulin secretion, the cytoplasmic domain of ICA512 is cleaved and relocated to the nucleus, where it stimulates the transcription of the insulin gene. The role of the other parts of the receptor in insulin secretion is yet to be unveiled. The structures of the intracellular pseudocatalytic and mature extracellular domains are known, but the transmembrane domain and several intracellular and extracellular parts of the receptor are poorly characterized. Moreover the overall structure of the receptor remains to be established. We started to address this issue studying by X-ray crystallography the structure of the mature ectodomain of ICA512 (ME ICA512) and variants thereof. The variants and crystallization conditions were chosen with the purpose of exploring putative association interfaces, metal binding sites and all other structural details that might help, in subsequent works, to build a model of the entire receptor. Several structural features were clarified and three main different association modes of ME ICA512 were identified. The results provide essential pieces of information for the design of new experiments aimed to assess the structure in vivo.
PLoS ONE 01/2011; 6(9):e24191. · 4.09 Impact Factor
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ABSTRACT: The insulin granule was previously thought of as merely a container, but accumulating evidence suggests that it also acts as a signaling node. Regulatory pathways intersect at but also originate from the insulin granule membrane. Examples include the small G-proteins Rab3a and Rab27a, which influence granule movement, and the transmembrane proteins (tyrosine phosphatase receptors type N) PTPRN and PTPRN2, which upregulate β-cell transcription and proliferation. In addition, many cosecreted compounds possess regulatory functions, often related to energy metabolism. For instance, ATP and γ-amino butyric acid (GABA) modulate insulin and glucagon secretion, respectively; C-peptide protects β-cells and kidney cells; and amylin reduces gastric emptying and food intake via the brain. In this paper, we review the current knowledge of the insulin granule proteome and discuss its regulatory functions.
Trends in Endocrinology and Metabolism 10/2010; 21(10):599-609. · 8.11 Impact Factor
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ABSTRACT: SNAP25 and syntaxin-1 are core proteins of the exocytosis machinery for insulin granules. Takahashi et al. (2010) show that the distribution and kinetics of the SNAP25/syntaxin-1 complex assembly play a key role in regulating the first and second phase of insulin release.
Cell metabolism 07/2010; 12(1):5-6. · 17.35 Impact Factor
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Sandra Schubert,
Klaus-Peter Knoch,
Joke Ouwendijk,
Shabaz Mohammed,
Yury Bodrov,
Melanie Jäger,
Anke Altkrüger,
Carolin Wegbrod,
Marvin E Adams,
Yong Kim,
Stanley C Froehner,
Ole N Jensen,
Yannis Kalaidzidis, Michele Solimena
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ABSTRACT: The molecular basis for the interaction of insulin granules with the cortical cytoskeleton of pancreatic β-cells remains unknown. We have proposed that binding of the granule protein ICA512 to the PDZ domain of β2-syntrophin anchors granules to actin filaments and that the phosphorylation/dephosphorylation of β2-syntrophin regulates this association. Here we tested this hypothesis by analyzing INS-1 cells expressing GFP-β2-syntrophin through the combined use of biochemical approaches, imaging studies by confocal and total internal reflection fluorescence microscopy as well as electron microscopy. Our results support the notion that β2-syntrophin restrains the mobility of cortical granules in insulinoma INS-1 cells, thereby reducing insulin secretion and increasing insulin stores in resting cells, while increasing insulin release upon stimulation. Using mass spectrometry, in vitro phosphorylation assays and β2-syntrophin phosphomutants we found that phosphorylation of β2-syntrophin on S75 near the PDZ domain decreases its binding to ICA512 and correlates with increased granule motility, while phosphorylation of S90 has opposite effects. We further show that Cdk5, which regulates insulin secretion, phosphorylates S75. These findings provide mechanistic insight into how stimulation displaces insulin granules from cortical actin, thus promoting their motility and exocytosis.
PLoS ONE 01/2010; 5(9):e12929. · 4.09 Impact Factor
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ABSTRACT: The inducible Cre-lox system is a valuable tool to study gene function in a spatial and time restricted fashion in mouse models. This strategy relies on the limited background activity of the modified Cre recombinase (CreER) in the absence of its inducer, the competitive estrogen receptor ligand, tamoxifen. The RIP-CreER mouse (Tg (Ins2-cre/Esr1) 1Dam) is among the few available β-cell specific CreER mouse lines and thus it has been often used to manipulate gene expression in the insulin-producing cells of the endocrine pancreas.
Here, we report the detection of tamoxifen-independent Cre activity as early as 2 months of age in RIP-CreER mice crossed with three distinct reporter strains.
Evidence of Cre-mediated recombination of floxed alleles even in the absence of tamoxifen administration should warrant cautious use of this mouse for the study of pancreatic β-cells.
PLoS ONE 01/2010; 5(10):e13533. · 4.09 Impact Factor
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ABSTRACT: Pancreatic beta-cells are the sole source of insulin, the major hormonal regulator of glycaemia. In physiological and pathological conditions with increased insulin demand, beta-cells adjust their insulin output either through increased insulin secretory granule (ISG) biogenesis and secretion, or hyperplasia. Failure of these compensatory mechanisms eventually results in hyperglycaemia and diabetes mellitus. Both of these major adaptive behaviours are positively regulated by several extrinsic factors, such as glucose, GLP-1, insulin and growth hormones (GH). Still unclear, however, it is how beta-cells in response to these stimuli opt for one or the other strategy at a given time. Here we review recent advances concerning the factors and pathways that enhance ISG biogenesis and beta-cell replication, and propose the existence of 'switch factors' that play a key role in regulating the shift between these two adaptive responses.
Diabetes Obesity and Metabolism 11/2009; 11 Suppl 4:54-64. · 3.38 Impact Factor
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ABSTRACT: Glucose and cAMP-inducing agents such as 3-isobutyl-1-methylxanthine (IBMX) rapidly change the expression profile of insulin-producing pancreatic beta-cells mostly through post-transcriptional mechanisms. A thorough analysis of these changes, however, has not yet been performed. By combining two-dimensional differential gel electrophoresis and mass spectrometry, we identified 165 spots, corresponding to 78 proteins, whose levels significantly change after stimulation of the beta-cell model INS-1 cells with 25 mM glucose + 1 mM IBMX for 2 h. Changes in the expression of selected proteins were verified by one- and two-dimensional immunoblotting. Most of the identified proteins are novel targets of rapid regulation in beta-cells. The transcription inhibitor actinomycin D failed to block changes in two-thirds of the spots, supporting their post-transcriptional regulation. More spots changed in response to IBMX than to glucose alone conceivably because of phosphorylation. Fourteen mRNA- binding proteins responded to stimulation, thus representing the most prominent class of rapidly regulated proteins. Bioinformatics analysis indicated that the mRNA 5'- and 3'-untranslated regions of 22 regulated proteins contain potential binding sites for polypyrimidine tract-binding protein 1, which promotes mRNA stability and translation in stimulated beta-cells. Overall our findings support the idea that mRNA-binding proteins play a major role in rapid adaptive changes in insulin-producing cells following their stimulation with glucose and cAMP-elevating agents.
Molecular & Cellular Proteomics 11/2008; 8(3):393-408. · 7.40 Impact Factor
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ABSTRACT: Insulin maintains homeostasis of glucose by promoting its uptake into cells from the blood. Hyperglycemia triggers secretion of insulin from pancreatic beta-cells. This process is mediated by secretory granule exocytosis. However, how beta-cells keep granule stores relatively constant is still unknown. ICA512 is an intrinsic granule membrane protein, whose cytosolic domain binds beta2-syntrophin, an F-actin-associated protein, and is cleaved upon granule exocytosis. The resulting cleaved cytosolic fragment, ICA512-CCF, reaches the nucleus and up-regulates the transcription of granule genes, including insulin and ICA512. Here, we show that ICA512-CCF also dimerizes with intact ICA512 on granules, thereby displacing it from beta2-syntrophin. This leads to increased granule mobility and insulin release. Based on these findings, we propose a model whereby the generation of ICA512-CCF first amplifies insulin secretion. The ensuing reduction of granule stores would then increase the probability of newly generated ICA512-CCF to reach the nucleus and enhance granule biogenesis, thus allowing beta-cells to constantly adjust production of granules to their storage size and consumption. Pharmacological modulation of these feedback loops may alleviate deficient insulin release in diabetes.
Journal of Biological Chemistry 11/2008; 283(48):33719-29. · 4.77 Impact Factor
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ABSTRACT: Islet cell autoantigen of 69kDa (ICA69) is a small GTPase-binding protein of unknown function. ICA69 is enriched in the Golgi complex and its N-terminal half contains a BAR domain, a module that can bind/bend membranes and interacts with phospholipids. Here we show that in insulinoma INS-1 cells ICA69 binds to the small GTPase Rab2, which regulates the transport of COPI vesicles between the endoplasmic reticulum and the Golgi complex. Rab2 binds to ICA69 in a GTP-dependent fashion and recruits it to membranes. Over-expression of either Rab2 or ICA69 in INS-1 cells results in a phenotype characterized by: (i) impaired anterograde transport of the secretory granule protein precursors pro-ICA512 and chromogranin A; (ii) reduction of stimulated insulin secretion. Taken together, these data identify ICA69 as a novel Rab2 effector and point to its role in regulating the early transport of insulin secretory granule proteins.
European Journal of Cell Biology 05/2008; 87(4):197-209. · 2.81 Impact Factor
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ABSTRACT: Changes in metabolic demands dynamically regulate the total mass of adult pancreatic beta-cells to adjust insulin secretion and preserve glucose homeostasis. Glucose itself is a major regulator of beta-cell proliferation by inducing insulin secretion and activating beta-cell insulin receptors. Here, we show that islet cell autoantigen 512 (ICA512)/IA-2, an intrinsic tyrosine phosphatase-like protein of the secretory granules, activates a complementary pathway for beta-cell proliferation. On granule exocytosis, the ICA512 cytoplasmic domain is cleaved and the resulting cytosolic fragment (ICA512-CCF) moves into the nucleus where it enhances the levels of phosphorylated STAT5 and STAT3, thereby inducing insulin gene transcription and granule biogenesis. We now show that knockdown of ICA512 decreases cyclin D1 levels and proliferation of insulinoma INS-1 cells, whereas beta-cell regeneration is reduced in partially pancreatectomized ICA512-/- mice. Conversely, overexpression of ICA512-CCF increases both cyclin D1 and D2 levels and INS-1 cell proliferation. Up-regulation of cyclin D1 and D2 by ICA512-CCF is affected by knockdown of STAT3 and STAT5, respectively, whereas it does not require insulin signaling. These results identify ICA512 as a regulator of cyclins D and beta-cell proliferation through STATs and may have implication for diabetes therapy.
Proceedings of the National Academy of Sciences 02/2008; 105(2):674-9. · 9.68 Impact Factor
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ABSTRACT: The Islets of Langerhans form a nutrient sensing network spread throughout the pancreas. They are tightly connected to the source organ, the intestine, and the target organs--liver, muscle, and fat cells. The expression of a unique set of proteins enables beta cells, the most frequent islet cell type, to detect elevated blood glucose levels and secrete insulin accordingly. Clustered beta-cells achieve tighter regulation of glucose-induced insulin secretion by coordination through cell surface proteins. They also adjust their secretory capacity and flow to avoid being damaged. The immediate reaction of the beta cell to nutrients is regulated by translational mechanisms, while longer term adaptations involve changes in transcription. Glucose increases overall protein synthesis in beta-cells but selectively boosts translation of some secretory proteins including insulin. This may be mediated through recognition of RNA motifs in the untranslated regions of those messengers. If essential molecular components of this nutrient sensing system are broken or fail due to repeated stress, beta cells malfunction, which on a larger scale manifest as diseases like diabetes mellitus.
Frontiers in Bioscience 02/2008; 13:7156-71. · 3.52 Impact Factor
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ABSTRACT: Secretory granules of neuroendocrine cells store and release peptide hormones and neuropeptides in response to various stimuli. Generation of granules from the Golgi complex involves the aggregation of cargo proteins and their sorting from non-regulated secretory molecules. Recent findings on knockout mice lacking individual granule constituents have challenged the hypothesis that an 'essential' protein for the assembly of these organelles exists, while studies on polypyrimidine tract-binding protein and ICA512/IA-2 have provided insight into the mechanisms for adjusting granule production in relation to stimulation and secretory activity.
Current Opinion in Cell Biology 09/2006; 18(4):365-70. · 12.90 Impact Factor
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ABSTRACT: Type 2 diabetes is a complex polygenic metabolic disorder of epidemic proportions. This review provides a brief overview of the susceptibility genes in type 2 diabetes that primarily affect pancreatic 3 cells, with emphasis on their function and most relevant polymorphisms. We focus on calpain 10, the only susceptibility gene identified thus far through a positional cloning approach in subjects with diabetes.
Endocrinology & Metabolism Clinics of North America 07/2006; 35(2):357-69, x. · 3.41 Impact Factor
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Hassan Mziaut,
Mirko Trajkovski,
Stephan Kersting,
Armin Ehninger,
Anke Altkrüger,
Régis P Lemaitre,
Darja Schmidt,
Hans-Detlev Saeger,
Myung-Shik Lee,
David N Drechsel,
Stefan Müller, Michele Solimena
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ABSTRACT: Nutrients and growth hormones promote insulin production and the proliferation of pancreatic beta-cells. An imbalance between ever-increasing metabolic demands and insulin output causes diabetes. Recent evidence indicates that beta-cells enhance insulin gene expression depending on their secretory activity. This signalling pathway involves a catalytically inactive receptor tyrosine phosphatase, ICA512, whose cytoplasmic tail is cleaved on glucose-stimulated exocytosis of insulin secretory granules and then moves into the nucleus, where it upregulates insulin transcription. Here, we show that the cleaved cytosolic fragment of ICA512 enhances the transcription of secretory granule genes (including its own gene) by binding to tyrosine phosphorylated signal transducers and activators of transcription (STAT) 5 and preventing its dephosphorylation. Sumoylation of ICA512 by the E3 SUMO ligase PIASy, in turn, may reverse this process by decreasing the binding of ICA512 to STAT5. These findings illustrate how the exocytosis of secretory granules, through a retrograde pathway that sustains STAT activity, converges with growth hormone signalling to induce adaptive changes in beta-cells in response to metabolic demands.
Nature Cell Biology 06/2006; 8(5):435-45. · 19.49 Impact Factor
