Lukas Alfons Huber

• Innsbruck Medical University

Entry and exit from quiescence require changes in cellular nutrient acquisition. How quiescent cells reduce nutrient uptake was unclear. Here, we demonstrate that cells entering quiescence select plasma membrane-resident amino acid (AA) transporters for endocytosis and lysosomal degradation, to match AA uptake with reduced translation. The endocyti...

The neurodevelopmental disorders Prader-Willi syndrome (PWS) and Schaaf-Yang syndrome (SYS) both arise from genomic alterations within human chromosome 15q11–q13. A deletion of the SNORD116 cluster, encoding small nucleolar RNAs, or frameshift mutations within MAGEL2 result in closely related phenotypes in individuals with PWS or SYS, respectively....

Seasonally circulating viruses, such as Influenza, as well as newly emerging viruses and variants thereof, and waning immunity urge the need for safe, easy-to-use and inexpensive drugs to protect from these challenges. To prevent transmission of these viruses and subsequent excessive inflammatory reactions on mucous membranes, we tested the efficac...

Precision oncology approaches for patients with colorectal cancer (CRC) continue to lag behind other solid cancers. Functional precision oncology—a strategy that is based on perturbing primary tumor cells from cancer patients—could provide a road forward to personalize treatment. We extend this paradigm to measuring proteome activity landscapes by...

Introduction To explore whether the reported lower pathogenicity in infected individuals of variant of concern (VoC) Omicron and its current subvariants compared to VoC Delta may be related to fundamental differences in the initial virus-tissue interaction, we assessed their ability to penetrate, replicate and cause damage in a human 3D respiratory...

Delta-like homolog 1 (Dlk1), an inhibitor of adipogenesis, controls the cell fate of adipocyte progenitors. Experimental data presented here identify two independent regulatory mechanisms, transcriptional and translational, by which Ifrd1 (TIS7) and its orthologue Ifrd2 (SKMc15) regulate Dlk1 levels. Mice deficient in both Ifrd1 and Ifrd2 (dKO) had...

Congenital glucose-galactose malabsorption is a rare autosomal recessive disorder caused by mutations in SLC5A1 encoding the apical sodium/glucose cotransporter SGLT1. We present clinical and molecular data from eleven affected individuals with congenital glucose-galactose malabsorption from four unrelated, consanguineous Turkish families. Early re...

Heterozygous mutations in the gene encoding RagD GTPase were shown to cause a novel autosomal dominant condition characterized by kidney tubulopathy and cardiomyopathy. We previously demonstrated that RagD, and its paralogue RagC, mediate a non-canonical mTORC1 signaling pathway that inhibits the activity of TFEB and TFE3, transcription factors of...

Heterozygous mutations in the gene encoding RagD GTPase were shown to cause a novel autosomal dominant condition characterized by kidney tubulopathy and cardiomyopathy. We previously demonstrated that RagD, and its paralogue RagC, mediate a non-canonical mTORC1 signaling pathway that inhibits the activity of TFEB and TFE3, transcription factors of...

Background: Calcific aortic valve disease (CAVD) is characterized by a phenotypic switch of valvular interstitial cells to bone-forming cells. Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors at the interface between innate immunity and tissue repair. Type I interferons (IFNs) are not only crucial for an adequa...

New SARS-CoV-2 variants of concern (VOCs) and waning immunity illustrate that quick and easy-to-use agents are needed to prevent infection. To protect from viral transmission and subsequent inflammatory reactions, we applied GlyperA™, a novel antimicrobial formulation that can be used as mouth gargling solution or as nasal spray, to highly differen...

Objective: In brown adipose tissue (iBAT), the balance between lipid/glucose uptake and lipolysis is tightly regulated by insulin signaling. Downstream of the insulin receptor, PDK1 and mTORC2 phosphorylate AKT, which activates glucose uptake and lysosomal mTORC1 signaling. The latter requires the late endosomal/lysosomal adaptor and MAPK and mTOR...

Lysosomes are highly dynamic organelles that regulate metabolic signaling pathways by recruiting cytosolic proteins to platforms on their limiting membrane. To identify new proteins recruited to these platforms, we performed a proximity-dependent labelling screen using as bait a component of the late endosomal/lysosomal adaptor and MAPK and mTOR ac...

The transcription factor TFEB is a master regulator of lysosomal biogenesis and autophagy¹. The phosphorylation of TFEB by the mechanistic target of rapamycin complex 1 (mTORC1)2–5 is unique in its mTORC1 substrate recruitment mechanism, which is strictly dependent on the amino acid-mediated activation of the RagC GTPase activating protein FLCN6,7....

Epithelial polarization and polarized cargo transport are highly coordinated and interdependent processes. In our search for novel regulators of epithelial polarization and protein secretion, we used a genome-wide CRISPR/Cas9 screen and combined it with an assay based on fluorescence-activated cell sorting (FACS) to measure the secretion of the api...

Here, we describe a detailed step-by-step protocol for the detection of phosphoproteins in two-dimensional difference gel electrophoresis (2D-DIGE) gels. A standard 2D-DIGE protocol is combined with subsequent post-staining with phosphospecific fluorescent dye. The combination of these two methods complements 2D-DIGE-based proteome profiling by flu...

Background Despite major advances in the development of targeted therapies, precision (immuno)oncology approaches for patients with colorectal cancer continue to lag behind other solid cancers. Functional precision oncology – a strategy that is based on perturbing primary tumor cells from cancer patients with drugs – could provide an alternate road...

The transcription factor TFEB is a master regulator of lysosomal biogenesis and autophagy. The phosphorylation of TFEB by the mechanistic target of rapamycin complex 1 (mTORC1) is unique in its mTORC1 substrate recruitment mechanism, which is strictly dependent on the amino-acid-mediated activation of the RagC GAP FLCN. TFEB lacks the TOR signaling...

In brown adipose tissue (iBAT), the balance of lipid/glucose uptake and lipolysis is regulated by insulin signaling. Downstream of the insulin receptor, PDK1 and mTORC2 phosphorylate AKT, which activates glucose uptake and lysosomal mTORC1 signaling. The latter requires the late endosomal/lysosomal adaptor and MAPK and mTOR activator (LAMTOR/Ragula...

Variants in the UNC45A cochaperone have been recently associated with a syndrome combining diarrhea, cholestasis, deafness, and bone fragility. Yet the mechanism underlying intestinal failure in UNC45A deficiency remains unclear. Here, biallelic variants in UNC45A were identified by next-generation sequencing in 6 patients with congenital diarrhea....

Epithelial polarization and polarized cargo transport are highly coordinated and interdependent processes. In our search for novel regulators of epithelial polarization and protein secretion, we used a genome-wide CRISPR/Cas9 screen and combined it with an assay based on fluorescence-activated cell sorting (FACS) to measure the secretion of the api...

Objectives Metabolic inflammation is a hallmark of obesity and related disorders, afflicting substantial morbidity and mortality to individuals worldwide. White visceral and subcutaneous adipose tissue not only serves as energy storage but also controls metabolism. Adipose tissue inflammation, commonly observed in human obesity, is considered a cri...

Inflammatory skin diseases, including atopic dermatitis (AD) and psoriasis, are increasing in populations worldwide. The treatment of patients with AD and other forms of skin inflammation is mainly based on the use of topical corticosteroids or calcineurin inhibitors, which can cause significant side effects with long-term use. Therefore, there is...

Complement-opsonized HIV-1 triggers efficient antiviral type I interferon (IFN) responses in dendritic cells (DCs), which play an important role in protective responses at the earliest stages in retroviral infection. In contrast, HIV-1 suppresses or escapes sensing by STING- and MAVS-associated sensors. Here, we identified a complement receptor-med...

Seizure threshold 2 (SZT2) is a component of the KICSTOR complex which, under catabolic conditions, functions as a negative regulator in the amino acid-sensing branch of mTORC1. Mutations in this gene cause a severe neurodevelopmental and epileptic encephalopathy whose main symptoms include epilepsy, intellectual disability, and macrocephaly. As SZ...

Dendritic cells (DCs), as well as complement, play a major role during human immunodeficiency virus 1 (HIV-1) entry and infection at mucosal sites. Together, DCs and complement are key points for understanding host defence against HIV-1 infection and for studying the impact of new drugs on the regulation of innate host-pathogen interactions and ada...

Biallelic STX3 variants were previously reported in five individuals with the severe congenital enteropathy, microvillus inclusion disease (MVID). Here, we provide a significant extension of the phenotypic spectrum caused by STX3 variants. We report ten individuals of diverse geographic origin with biallelic STX3 loss-of-function variants, identifi...

Mutations in the actin motor protein myosinVb (myo5b) cause aberrant apical cargo transport and the congenital enteropathy microvillus inclusion disease (MVID). Recently, missense mutations in myo5b were also associated with progressive familial intrahepatic cholestasis (MYO5B-PFIC). Here, we thoroughly characterized the ultrastructural and immuno-...

Background: Excessive inflammation triggered by a hitherto undescribed mechanism is a hallmark of severe SARS-CoV-2 infections and is associated with enhanced pathogenicity and mortality. Objective: Complement hyper activation promotes lung injury and was observed in patients suffering from MERS-CoV, SARS-CoV-1 and SARS-CoV-2 infections. Therefo...

Natural products and their structural analogues have historically made a major contribution to pharmacotherapy, especially for cancer and infectious diseases. Nevertheless, natural products also present challenges for drug discovery, such as technical barriers to screening, isolation, characterization and optimization, which contributed to a declin...

Myosin Vb (MYO5B) is a motor protein that facilitates protein trafficking and recycling in polarized cells by RAB11- and RAB8-dependent mechanisms. Biallelic MYO5B mutations are identified in the majority of patients with microvillus inclusion disease (MVID). MVID is an intractable diarrhea of infantile onset with characteristic histopathologic fin...

The nuclear factor kappa B (NF-κB) family of dimeric transcription factors regulates a wide range of genes by binding to their specific DNA regulatory sequences. NF-κB is an important therapeutic target linked to a number of cancers as well as autoimmune and inflammatory diseases. Therefore, effective high-throughput methods for the detection of NF...

The diagnosis of COVID-19 relies on the direct detection of SARS-CoV-2 RNA in respiratory specimens by RT-PCR. The pandemic spread of the disease caused an imbalance between demand and supply of materials and reagents needed for diagnostic purposes including swab sets. In a comparative effectiveness study, we conducted serial follow-up swabs in hos...

Ras GTPase-activating protein-binding proteins 1 and 2 (G3BP1 and G3BP2, respectively) are widely recognized as core components of stress granules (SGs). We report that G3BPs reside at the cytoplasmic surface of lysosomes. They act in a non-redundant manner to anchor the tuberous sclerosis complex (TSC) protein complex to lysosomes and suppress act...

Changes in size and abundance of late endocytic and autophagic organelles are increasingly appreciated as highly indicative of the physiological or pathological conditions of cells. Electron microscopy (EM) is unsurpassed in high-resolution imaging of both ultrastructural and immunocytochemical features of subcellular compartments. EM-based morphom...

Congenital diarrheal disorders (CDD) comprise > 50 monogenic entities featuring chronic diarrhea of early-onset, including defects in nutrient and electrolyte absorption, enterocyte polarization, enteroendocrine cell differentiation, and epithelial integrity. Diarrhea is also a predominant symptom in many immunodeficiencies, congenital disorders of...

The mechanistic target of rapamycin complex 1 (mTORC1) is a key metabolic hub that controls the cellular response to environmental cues by exerting its kinase activity on multiple substrates1–3. However, whether mTORC1 responds to diverse stimuli by differentially phosphorylating specific substrates is poorly understood. Here we show that transcrip...

Dendritic cells (DCs) possess intrinsic cellular defense mechanisms to specifically inhibit HIV-1 replication. In turn, HIV-1 has evolved strategies to evade innate immune sensing by DCs resulting in suboptimal maturation and poor antiviral immune responses. We previously showed that complement-opsonized HIV-1 (HIV-C) was able to efficiently infect...

How cells adjust nutrient transport across their membranes is incompletely understood. Previously, we have shown that S. cerevisiae broadly re-configures the nutrient transporters at the plasma membrane in response to amino acid availability, through endocytosis of sugar- and amino acid transporters (AATs) (Müller et al., 2015). A genome-wide scree...

How cells adjust nutrient transport across their membranes is incompletely understood. Previously, we have shown that S. cerevisiae broadly re-configures the nutrient transporters at the plasma membrane in response to amino acid availability, through endocytosis of sugar- and amino acid transporters (AATs) (Müller et al., 2015). A genome-wide scree...

How cells adjust nutrient transport across their membranes is incompletely understood. Previously, we have shown that S. cerevisiae broadly re-configures the nutrient transporters at the plasma membrane in response to amino acid availability, through endocytosis of sugar- and amino acid transporters (AATs) (Müller et al., 2015). A genome-wide scree...

Differentiated cells can re-enter the cell cycle to repair tissue damage via a series of discrete morphological and molecular stages coordinated by the cellular energetics regulator mTORC1. We previously proposed the term “paligenosis” to describe this conserved cellular regeneration program. Here, we detail a molecular network regulating mTORC1 du...

Biallelic loss‐of‐function mutations in the centrosomal pericentrin gene (PCNT) cause microcephalic osteodysplastic primordial dwarfism type II (MOPDII), which is characterized by extreme growth retardation, microcephaly, skeletal dysplasia, and dental anomalies. Life expectancy is reduced due to a high risk of cerebral vascular anomalies. Here, we...

The diagnosis of COVID-19 relies on the direct detection of SARS-CoV-2 RNA in respiratory specimens by RT-PCR. The pandemic spread of the disease caused an imbalance between demand and supply of materials and reagents needed for diagnostic purposes including swab sets. In a comparative effectiveness study, we conducted serial follow-up swabs in hos...

G3BP1 (Ras GTPase-activating protein-binding protein 1) is widely recognized as a core component of stress granules (SG), non-membranous RNA-protein-assemblies required for cellular survival under stress. We report that in the absence of SG, G3BP1 acts as lysosomal anchor of the Tuberous Sclerosis Complex (TSC) protein complex. By tethering the TSC...

Colorectal cancer (CRC), a cancer with 1.4 million new cases diagnosed annually worldwide, is refractory to immunotherapy (with the exception of a minority of tumors with microsatellite instability). This is somehow paradoxical as CRC is a cancer which we have shown is under immunologic control and that tumor-infiltrating lymphocytes represent a st...

Lysosomes are key cellular catabolic centers that also perform fundamental metabolic, signaling and quality control functions. Lysosomes are not static and they respond dynamically to intra‐ and extracellular stimuli triggering changes in organelle numbers, size and position. Such physical changes have a strong impact on lysosomal activity ultimate...

Biotechnology is an evolving research field that covers a broad range of topics. Here we aimed to evaluate the latest research literature, to identify prominent research themes, major contributors in terms of institutions, countries/regions, and journals. The Web of Science Core Collection online database was searched to retrieve biotechnology arti...

Biotechnology is an evolving research field that covers a broad range of topics. Here we aimed to evaluate the latest research literature, to identify prominent research themes, major contributors in terms of institutions, countries/regions, and journals. The Web of Science Core Collection online database was searched to retrieve biotechnology arti...

Late endosomal/lysosomal adaptor and MAPK and mTOR activator (LAMTOR/Ragulator) is a scaffold protein complex that anchors and regulates multiprotein signaling units on late endosomes/lysosomes. To identify LAMTOR‐modulated endolysosomal proteins, primary macrophages were derived from bone marrow of conditional knockout mice carrying a specific del...

Delta-like homolog 1 (DLK1), an inhibitor of adipogenesis, controls the cell fate of adipocyte progenitors. Here we identify two independent regulatory mechanisms, transcriptional and translational, by which TIS7 (IFRD1) and its orthologue SKMc15 (IFRD2) regulate DLK1 levels. Mice deficient in both TIS7 and SKMc15 (dKO) had severely reduced adipose...

Mechanisms that control lysosomal function are essential for cellular homeostasis. Lysosomes adapt in size and number to cellular needs but little is known about the underlying molecular mechanism. We demonstrate that the late endosomal/lysosomal multimeric BLOC-1 related complex (BORC) regulates size of these organelles via PIKfyve-dependent phosp...

B-cell development and function depend on stage-specific signaling through the B-cell antigen receptor (BCR). Signaling and intracellular trafficking of the BCR are connected, but the molecular mechanisms of this link are incompletely understood. Here, we investigated the role of the endosomal adaptor protein and member of the LAMTOR/Ragulator comp...

Although biological and pharmacological effects of dietary natural products have been intensively studied, there has been no bibliometric analysis performed on this research field up to now. The current study has aimed to identify and analyze the manuscripts on dietary natural products and their potential to influence health and disease including s...

Human LAMTOR2 deficiency is characterized by severe congenital neutropenia, growth failure, partial albinism, as well as B and T cell deficiencies (Bohn et al., Nat Med 2007). To determine the role of the endosomal adaptor LAMTOR2 in T cell development and homeostasis we used conditional knockout mouse models. Mx1-Cre-driven knockout of Lamtor2 res...

Complement system and dendritic cells (DCs) form – beside neutrophils and macrophages – the first line of defense to combat fungal infections. Therefore, we here studied interactions of these first immune elements with Aspergillus fumigatus lacking ß-1,3-glucans (fks1tetOnrep under repressed conditions) to mechanistically explain the mode of action...

Although biological and pharmacological effects of dietary natural products have been intensively studied, there has been no bibliometric analysis performed on this research field up to now. The current study has aimed to identify and analyze the manuscripts on dietary natural products and their potential to influence health and disease including s...

Background & aims: Inactivating mutations in myosin VB (MYO5B) cause microvillus inclusion disease (MVID), but the physiological cause of the diarrhea associated with this disease is unclear. We investigated whether loss of MYO5B results in aberrant expression of apical enterocyte transporters. Methods: We studied alterations in apical membrane...

Immunogold labeling of permeabilized whole‐mount cells or thin‐sectioned material is widely used for the subcellular localization of biomolecules at the high spatial resolution of electron microscopy (EM). Those approaches are well compatible with either three‐dimensional (3D) reconstruction of organelle morphology and antigen distribution or with...

Here, we describe the detailed step-by-step protocol for detection of phosphoproteins in two-dimensional difference gel electrophoresis (DIGE) gels. A standard DIGE protocol is combined with subsequent post-staining with phosphospecific fluorescent dye. The combination of these two methods complements DIGE-based proteome profiling by fluorescence d...

Signaling from lysosomes controls cellular clearance and energy metabolism. Lysosomal malfunction has been implicated in several pathologies, including neurodegeneration, cancer, infection, immunodeficiency, and obesity. Interestingly, many functions are dependent on the organelle position. Lysosomal motility requires the integration of extracellul...

Structure of human mTORC1 components The mTORC1 (mechanistic target of rapamycin complex 1) complex garners much attention as a signaling hub that coordinates input from growth-factor receptors and nutrient availability with metabolism and cell growth and proliferation. de Araujo et al. report the crystal structure of the LAMTOR (or “Ragulator”) co...

Familial hemophagocytic lymphohistiocytosis 5 (FHL5) is an autosomal recessive disease caused by mutations in STXBP2, coding for Munc18-2, which is required for SNARE-mediated membrane fusion. FHL5 causes hematologic and gastrointestinal symptoms characterized by chronic enteropathy that is reminiscent of microvillus inclusion disease (MVID). Howev...

Aims: Lp(a) concentrations represent a major cardiovascular risk factor and are almost entirely controlled by one single locus (LPA). However, many genetic factors in LPA governing the enormous variance of Lp(a) levels are still unknown. Since up to 70% of the LPA coding sequence are located in a difficult to access hypervariable copy number varia...

Microvillus Inclusion Disease (MVID) is a congenital enteropathy characterized by accumulation of vesiculo-tubular endomembranes in the subapical cytoplasm of enterocytes, historically termed "secretory granules". However, neither their identity nor pathophysiological significance is well defined. Using immunoelectron microscopy and tomography we s...

We identified two unrelated consanguineous families with three children affected by the rare association of congenital nephrotic syndrome diagnosed in the first days of life, of hypogonadism, and of prenatally detected adrenal calcifications, associated with congenital adrenal insufficiency in one case. Using exome sequencing and targeted Sanger se...

Background TPA Induced Sequence 7 acts as a transcriptional co-regulator controlling the expression of genes involved in differentiation of various cell types, including skeletal myoblasts. We and others have shown that TIS7 regulates adult myogenesis through MyoD, one of the essential myogenic regulatory factors. Results Here, we present data ide...

Autophagy mediates the (non-)selective bulk degradation of cytoplasm, protein aggregates, damaged organelles and certain pathogens. The endosomal membrane system uses multivesicular bodies (MVBs) to selectively deliver ubiquitinated membrane proteins together with extracellular components into lysosomes. Microautophagy (MA) and chaperone-mediated a...

Significance The transcription factor nuclear factor kappa B (NF-κB) plays a vital role in cellular immune, stress, and proliferative responses by regulating genes. To maintain correct execution of the genetic program and to prevent pathologies (e.g., chronic inflammation), the activation of NF-κB has to be transient and precisely controlled. We de...

Microvillus inclusion disease (MVID) is characterised by onset of intractable life-threatening watery diarrhoea during infancy. Transmission electron microscopy demonstrates shortening or absence of apical microvilli, pathognomonic microvillus inclusions in mature enterocytes and subapical accumulation of periodic acid-Schiff-positive granules or v...

Immortalized macrophage lines and primary macrophages display the ability to internalize small latex beads through the endocytic pathway. This protocol describes a simple and robust method for separating endocytic organelles from macrophages on a sucrose gradient, taking advantage of the significantly lower density of the organelles containing late...

Proteomic analysis of early and late endosomes has been constrained by the limited purity of the endosomal fractions that can be achieved by biochemical methods. Here we briefly review endocytic pathways, and then introduce fractionation strategies that have been used to improve the purity of isolated endosomes. In addition, we describe innovative...

Mutations in the motor protein Myosin Vb (Myo5B) or the soluble NSF attachment protein receptor Syntaxin 3 (Stx3) disturb epithelial polarity and cause microvillus inclusion disease (MVID), a lethal hereditary enteropathy affecting neonates. To understand the molecular mechanism of Myo5B and Stx3 interplay, we used genome editing to introduce a def...

Homogenization is the name given to the methodological steps necessary for releasing organelles and other cellular constituents as a free suspension of intact individual components. Most homogenization procedures used for mammalian cells (e.g., cavitation pump and Dounce homogenizer) rely on mechanical force to break the plasma membrane and may be...

Density gradient centrifugation is a common method for separating intracellular organelles. During centrifugation, organelles float or sediment until they reach their isopycnic position within the gradient. The density of an organelle depends on its content, size, shape, and the lipid:protein ratio. The degree of separation between different organe...

The endo/lysosomal system in cells provides membranous platforms to assemble specific signaling complexes and to terminate signal transduction, thus, is essential for physiological signaling. Endocytic organelles can significantly extend signaling of activated cell surface receptors, and may additionally provide distinct locations for the generatio...

Significance Microvillus inclusion disease (MVID) is a rare intestinal enteropathy resulting in severe diarrhoea in neonates. Here, we have generated an intestine-specific knockout mouse model for Myosin Vb, the gene causing MVID in the majority of human patients. Our mouse model completely recapitulates the intestinal human MVID phenotype, includi...

Objectives & Study: Microvillus inclusion disease (MVID) is characterized by severe and persistent congenital diarrhea. Patients are dependent on total parenteral nutrition (TPN) unless treated by intestinal transplantation. The pathological hallmarks are loss of brush border microvilli, secretory granules in the subapical cytoplasm of enterocytes...

The late endosomal adaptor protein LAMTOR2/p14 is essential for tissue homeostasis by controlling MAPK and mTOR signaling, which in turn regulate cell growth and proliferation, migration and spreading. Moreover, LAMTOR2 critically controls architecture and function of the endocytic system, including EGFR degradation in lysosomes, positioning of lat...