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Advances in Clinical Chemistry 2024Congenital disorders of glycosylation (CDG) are one of the fastest growing groups of inborn errors of metabolism, comprising over 160 described diseases to this day. CDG... (Review)
Review
Congenital disorders of glycosylation (CDG) are one of the fastest growing groups of inborn errors of metabolism, comprising over 160 described diseases to this day. CDG are characterized by a dysfunctional glycosylation process, with molecular defects localized in the cytosol, the endoplasmic reticulum, or the Golgi apparatus. Depending on the CDG, N-glycosylation, O-glycosylation and/or glycosaminoglycan synthesis can be affected. Various proteins, lipids, and glycosylphosphatidylinositol anchors bear glycan chains, with potential impacts on their folding, targeting, secretion, stability, and thus, functionality. Therefore, glycosylation defects can have diverse and serious clinical consequences. CDG patients often present with a non-specific, multisystemic syndrome including neurological involvement, growth delay, hepatopathy and coagulopathy. As CDG are rare diseases, and typically lack distinctive clinical signs, biochemical and genetic testing bear particularly important and complementary diagnostic roles. Here, after a brief introduction on glycosylation and CDG, we review historical and recent findings on CDG biomarkers and associated analytical techniques, with a particular emphasis on those with relevant use in the specialized clinical chemistry laboratory. We provide the reader with insights and methods which may help them properly assist the clinician in navigating the maze of glycosylation disorders.
Topics: Humans; Congenital Disorders of Glycosylation; Glycosylation; Biomarkers
PubMed: 38762238
DOI: 10.1016/bs.acc.2024.03.001 -
The Journal of Biological Chemistry Jun 2024The stepwise addition of monosaccharides to N-glycans attached to client proteins to generate a repertoire of mature proteins involves a concerted action of many...
The stepwise addition of monosaccharides to N-glycans attached to client proteins to generate a repertoire of mature proteins involves a concerted action of many glycosidases and glycosyltransferases. Here, we report that Golgi α-mannosidase II (GMII), a pivotal enzyme catalyzing the first step in the conversion of hybrid- to complex-type N-glycans, is activated by Zn supplied by the early secretory compartment-resident ZNT5-ZNT6 heterodimers (ZNT5-6) and ZNT7 homodimers (ZNT7). Loss of ZNT5-6 and ZNT7 function results in marked accumulation of hybrid-type and complex/hybrid glycans with concomitant reduction of complex- and high-mannose-type glycans. In cells lacking the ZNT5-6 and ZNT7 functions, the GMII activity is substantially decreased. In contrast, the activity of its homolog, lysosomal mannosidase (LAMAN), is not decreased. Moreover, we show that the growth of pancreatic cancer MIA PaCa-2 cells lacking ZNT5-6 and ZNT7 is significantly decreased in a nude mouse xenograft model. Our results indicate the integral roles of ZNT5-6 and ZNT7 in N-glycosylation and highlight their potential as novel target proteins for cancer therapy.
Topics: Humans; Glycosylation; Cation Transport Proteins; Animals; Zinc; Mice; Golgi Apparatus; Mannosidases; Polysaccharides; Cell Line, Tumor; Mice, Nude; Zinc Transporter 8
PubMed: 38762179
DOI: 10.1016/j.jbc.2024.107378 -
The Plant Journal : For Cell and... May 2024The pollen viability directly affects the pollination process and the ultimate grain yield of rice. Here, we identified that the MORN motif-containing proteins, OsMORN1...
The pollen viability directly affects the pollination process and the ultimate grain yield of rice. Here, we identified that the MORN motif-containing proteins, OsMORN1 and OsMORN2, had a crucial role in maintaining pollen fertility. Compared with the wild type (WT), the pollen viability of the osmorn1 and osmorn2 mutants was reduced, and pollen germination was abnormal, resulting in significantly lower spikelet fertility, seed-setting rate, and grain yield per plant. Further investigation revealed that OsMORN1 was localized to the Golgi apparatus and lipid droplets. Lipids associated with pollen viability underwent alterations in osmorn mutants, such as the diacylglyceride (18:3_18:3) was 5.1-fold higher and digalactosyldiacylglycerol (18:2_18:2) was 5.2-fold lower in osmorn1, while the triacylglycerol (TG) (16:0_18:2_18:3) was 8.3-fold higher and TG (16:0_18:1_18:3) was 8.5-fold lower in osmorn2 than those in WT. Furthermore, the OsMORN1/2 was found to be associated with rice cold tolerance, as osmorn1 and osmorn2 mutants were more sensitive to chilling stress than WT. The mutants displayed increased hydrogen peroxide accumulation, reduced antioxidant enzyme activities, elevated malondialdehyde content, and a significantly decreased seedling survival rate. Lipidomics analysis revealed distinct alterations in lipids under low temperature, highlighting significant changes in TG (18:2_18:3_18:3) and TG (18:4_18:2_18:2) in osmorn1, TG (16:0_18:2_18:2) and PI (17:2_18:3) in osmorn2 compared to the WT. Therefore, it suggested that OsMORN1 and OsMORN2 regulate both pollen viability and cold tolerance through maintaining lipid homeostasis.
PubMed: 38761113
DOI: 10.1111/tpj.16812 -
Molecular and Cellular Biology 2024SREBP transcription factors are central regulators of lipid metabolism. Their proteolytic activation requires ER to the Golgi translocation and subsequent cleavage by...
SREBP transcription factors are central regulators of lipid metabolism. Their proteolytic activation requires ER to the Golgi translocation and subsequent cleavage by site-1-protease (S1P). Produced as a proprotein, S1P undergoes autocatalytic cleavage from its precursor S1P to mature S1P form. Here, we report that SPRING (previously C12ORF29) and S1P interact through their ectodomains, and that this facilitates the autocatalytic cleavage of S1P into its mature S1P form. Reciprocally, we identified a S1P recognition-motif in SPRING and demonstrate that S1P-mediated cleavage leads to secretion of the SPRING ectodomain in cells, and in liver-specific knockout (LKO) mice transduced with AAV-mSpring. By reconstituting SPRING variants into SPRING cells we show that the SPRING ectodomain supports proteolytic maturation of S1P and SREBP signaling, but that S1P-mediated SPRING cleavage is not essential for these processes. Absence of SPRING modestly diminishes proteolytic maturation of S1P and trafficking of S1P to the Golgi. However, despite reaching the Golgi in SPRING cells, S1P fails to rescue SREBP signaling. Remarkably, whereas SREBP signaling was severely attenuated in SPRING cells and LKO mice, that of ATF6, another S1P substrate, was unaffected in these models. Collectively, our study positions SPRING as a dedicated licensing factor for SREBP-specific activation by S1P.
Topics: Animals; Mice; Mice, Knockout; Golgi Apparatus; Humans; Proprotein Convertases; Serine Endopeptidases; Signal Transduction; HEK293 Cells; Liver; Proteolysis; Endoplasmic Reticulum; Sterol Regulatory Element Binding Proteins
PubMed: 38747374
DOI: 10.1080/10985549.2024.2348711 -
Nature Communications May 2024A key mechanism employed by plants to adapt to salinity stress involves maintaining ion homeostasis via the actions of ion transporters. While the function of cation...
A key mechanism employed by plants to adapt to salinity stress involves maintaining ion homeostasis via the actions of ion transporters. While the function of cation transporters in maintaining ion homeostasis in plants has been extensively studied, little is known about the roles of their anion counterparts in this process. Here, we describe a mechanism of salt adaptation in plants. We characterized the chloride channel (CLC) gene AtCLCf, whose expression is regulated by WRKY transcription factor under salt stress in Arabidopsis thaliana. Loss-of-function atclcf seedlings show increased sensitivity to salt, whereas AtCLCf overexpression confers enhanced resistance to salt stress. Salt stress induces the translocation of GFP-AtCLCf fusion protein to the plasma membrane (PM). Blocking AtCLCf translocation using the exocytosis inhibitor brefeldin-A or mutating the small GTPase gene AtRABA1b/BEX5 (RAS GENES FROM RAT BRAINA1b homolog) increases salt sensitivity in plants. Electrophysiology and liposome-based assays confirm the Cl/H antiport function of AtCLCf. Therefore, we have uncovered a mechanism of plant adaptation to salt stress involving the NaCl-induced translocation of AtCLCf to the PM, thus facilitating Cl removal at the roots, and increasing the plant's salinity tolerance.
Topics: Arabidopsis; Cell Membrane; Salt Stress; Arabidopsis Proteins; Golgi Apparatus; Chloride Channels; Gene Expression Regulation, Plant; Protein Transport; Salt Tolerance; Sodium Chloride; Plants, Genetically Modified
PubMed: 38729926
DOI: 10.1038/s41467-024-48234-z -
Molecular Neurobiology May 2024Hexanucleotide repeat expansions (HREs) in the chromosome 9 open reading frame 72 (C9orf72) gene are the most frequent genetic cause of amyotrophic lateral sclerosis...
Hexanucleotide repeat expansions (HREs) in the chromosome 9 open reading frame 72 (C9orf72) gene are the most frequent genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Both are debilitating neurodegenerative conditions affecting either motor neurons (ALS) in the brain and spinal cord or neurons in the frontal and/or temporal cortical lobes (FTD). HREs undergo repeat-associated non-ATG (RAN) translation on both sense and anti-sense strands, generating five distinct dipeptide repeat proteins (DPRs), poly-GA, -GR, -GP, -PA and -PR. Perturbed proteostasis is well-recognised in ALS pathogenesis, including processes affecting the endoplasmic reticulum (ER) and Golgi compartments. However, these mechanisms have not been well characterised for C9orf72-mediated ALS/FTD. In this study we demonstrate that C9orf72 DPRs polyGA, polyGR and polyGP (× 40 repeats) disrupt secretory protein transport from the ER to the Golgi apparatus in neuronal cells. Consistent with this finding, these DPRs also induce fragmentation of the Golgi apparatus, activate ER stress, and inhibit the formation of the omegasome, the precursor of the autophagosome that originates from ER membranes. We also demonstrate Golgi fragmentation in cells undergoing RAN translation that express polyGP. Furthermore, dysregulated ER-Golgi transport was confirmed in C9orf72 patient dermal fibroblasts. Evidence of aberrant ER-derived vesicles in spinal cord motor neurons from C9orf72 ALS patients compared to controls was also obtained. These data thus confirm that ER proteostasis and ER-Golgi transport is perturbed in C9orf72-ALS in the absence of protein over-expression. Hence this study identifies novel molecular mechanisms associated with the ER and Golgi compartments induced by the C9orf72 HRE.
PubMed: 38722513
DOI: 10.1007/s12035-024-04187-4 -
Frontiers in Cell and Developmental... 2024The Golgi apparatus plays a crucial role in lysosome biogenesis and the delivery of lysosomal enzymes, essential for maintaining cellular homeostasis and ensuring cell... (Review)
Review
The Golgi apparatus plays a crucial role in lysosome biogenesis and the delivery of lysosomal enzymes, essential for maintaining cellular homeostasis and ensuring cell survival. Deficiencies in Golgi structure and function can profoundly impact lysosomal homeostasis, leading to various lysosomal storage diseases and neurodegenerative disorders. In this review, we highlight the role of the Golgi Reassembly Stacking Proteins (GRASPs) in the formation and function of the Golgi apparatus, emphasizing the current understanding of the association between the Golgi apparatus, lysosomes, and lysosomal storage diseases. Additionally, we discuss how Golgi dysfunction leads to the secretion of lysosomal enzymes. This review aims to serve as a concise resource, offering insights into Golgi structure, function, disease-related defects, and their consequential effects on lysosomal biogenesis and function. By highlighting Golgi defects as an underappreciated contributor to lysosomal dysfunction across various diseases, we aim to enhance comprehension of these intricate cellular processes.
PubMed: 38721528
DOI: 10.3389/fcell.2024.1386149 -
Science Advances May 2024Mutations in the gene encoding lamins A/C cause an array of tissue-selective diseases, with the heart being the most commonly affected organ. Despite progress in...
Mutations in the gene encoding lamins A/C cause an array of tissue-selective diseases, with the heart being the most commonly affected organ. Despite progress in understanding the perturbations emanating from mutations, an integrative understanding of the pathogenesis underlying cardiac dysfunction remains elusive. Using a novel conditional deletion model capable of translatome profiling, we observed that cardiomyocyte-specific deletion in adult mice led to rapid cardiomyopathy with pathological remodeling. Before cardiac dysfunction, -deleted cardiomyocytes displayed nuclear abnormalities, Golgi dilation/fragmentation, and CREB3-mediated stress activation. Translatome profiling identified MED25 activation, a transcriptional cofactor that regulates Golgi stress. Autophagy is disrupted in the hearts of these mice, which can be recapitulated by disrupting the Golgi. Systemic administration of modulators of autophagy or ER stress significantly delayed cardiac dysfunction and prolonged survival. These studies support a hypothesis wherein stress responses emanating from the perinuclear space contribute to the cardiomyopathy development.
Topics: Animals; Lamin Type A; Mice; Nuclear Envelope; Cardiomyopathies; Myocytes, Cardiac; Autophagy; Stress, Physiological; Disease Models, Animal; Endoplasmic Reticulum Stress; Golgi Apparatus; Mice, Knockout
PubMed: 38718107
DOI: 10.1126/sciadv.adh0798 -
Current Opinion in Cell Biology Jun 2024Vesicle transport at the Golgi apparatus is a well-described process, and the major protein components involved have been identified. This includes the coat proteins... (Review)
Review
Vesicle transport at the Golgi apparatus is a well-described process, and the major protein components involved have been identified. This includes the coat proteins that function in cargo sorting and vesicle formation, and the proteins that mediate the downstream events of vesicle tethering and membrane fusion. However, despite this knowledge, there remain significant gaps in our mechanistic understanding of these processes which includes how they are coordinated in space and time. In this review we discuss recent advances that have provided new insights into the mechanisms of Golgi trafficking, focussing on vesicle formation and cargo sorting, and vesicle tethering and fusion. These studies point to a high degree of spatial organisation of trafficking components at the Golgi and indicate an inherent plasticity of trafficking. Going forward, further advancements in technology and more sophisticated functional assays are expected to yield greater understanding of the mechanisms that govern Golgi trafficking events.
Topics: Golgi Apparatus; Humans; Animals; Protein Transport; Biological Transport; Transport Vesicles; Membrane Fusion
PubMed: 38705050
DOI: 10.1016/j.ceb.2024.102365 -
Journal of the American Chemical Society May 2024Cholesterol-rich membranes play a pivotal role in cancer initiation and progression, necessitating innovative approaches to target these membranes for cancer inhibition....
Cholesterol-rich membranes play a pivotal role in cancer initiation and progression, necessitating innovative approaches to target these membranes for cancer inhibition. Here we report the first case of unnatural peptide () assemblies capable of depleting cholesterol and inhibiting cancer cells. Peptide self-assembles into micelles and is rapidly taken up by cancer cells, especially when combined with an acute cholesterol-depleting agent (MβCD). Click chemistry has confirmed that depletes cell membrane cholesterol. It localizes in membrane-rich organelles, including the endoplasmic reticulum, Golgi apparatus, and lysosomes. Furthermore, potently inhibits malignant cancer cells, working synergistically with cholesterol-lowering agents. Control experiments have confirmed that C-terminal capping and unnatural amino acid residues (i.e., BiP) are essential for both cholesterol depletion and potent cancer cell inhibition. This work highlights unnatural peptide assemblies as a promising platform for targeting the cell membrane in controlling cell fates.
Topics: Humans; Cholesterol; Peptides; Antineoplastic Agents; Cell Line, Tumor; Cell Membrane; Cell Proliferation
PubMed: 38701349
DOI: 10.1021/jacs.4c03101