Project description:Androgen receptor (AR) plays an essential role in normal prostate development and prostate cancer (PCa) progression. To understand the role of AR at the single-cell level, we performed single-cell transcriptome analysis on PCa cells stimulated with androgen and antiandrogen to reconstruct the dynamic and direct AR transcriptional network. Our work reveals that androgen stimulates the ER and Golgi stress response , promoting secreting protein trafficking, and inhibiting cell apoptosis. Moreover, we identify an ER-to-Golgi protein vesicle-mediated transport gene signature essential for maximal androgen-mediated ER-Golgi trafficking, cell proliferation, and association with PCa prognosis and progression. Notably, we show that AR collaborates with CREB3L2, XXX, to coordinately promote ER-Golgi trafficking of Golgi enzyme Mannosidase II and PCa cell survival. Finally, we show the inhibition of the ER-Golgi transport process with Brefeldin A leads to tumor regression. Our study collectively reveals the heterogeneity of PCa cell transcriptional response to androgen stimulation, demonstrates a functional role for increased ER-Golgi trafficking process, and provides a mechanism for how the process is augmented in PCa as well as the potential of targeting may provide novel treatment strategies.
Project description:Compelling evidence indicates that defects in nucleocytoplasmic transport contribute to the pathogenesis of amyotrophic lateral sclerosis (ALS). In particular, hexanucleotide (G4C2) repeat expansions in C9orf72, the most common cause of genetic ALS, have a widespread impact on the transport machinery that regulates the nucleocytoplasmic distribution of proteins and RNAs, thereby affecting their functions. We have previously reported that the expression of G4C2 hexanucleotide repeats in cultured human and mouse cells caused a marked accumulation of poly(A) mRNAs in cell nuclei, suggesting that mRNA trafficking is impaired by expanded C9orf72-ALS repeats. To further characterize the process, in this work we set out to systematically identify the specific mRNAs that are altered in their nucleocytoplasmic distribution in the presence of C9orf72-ALS repeats. Results from RNAseq profiling of nuclear and cytoplasmic RNA fractions obtained from cells expressing G4C231 repeats show a significant accumulation of mRNAs in the nuclei of G4C231 cells, further suggesting that nuclear retention of mRNAs is a major effect of C9orf72 expanded repeats expression. Interestingly, pathway analysis shows that mRNAs involved in ER-to-Golgi trafficking are particularly enriched among the identified mRNAs. Most importantly, functional studies in cultured cells and Drosophila indicate that the membrane trafficking route regulated by ARFGAP1, a GTPase-activating protein that associates with Golgi, is specifically affected by expanded C9orf72 repeats, as well as by C9orf72-related dipeptide repeat proteins (C9-DPRs), pointing to ER-to-Golgi vesicle-mediated transport as a target of C9orf72 toxicity.
Project description:Impaired proinsulin processing is observed in both type 1 and type 2 diabetes. We have previously shown that reductions in endoplasmic reticulum (ER) calcium (Ca2+) in the pancreatic β cell arising from impaired activity of the Sarcoendoplasmic Reticulum Ca2+ ATPase (SERCA) pump are associated with increased proinsulin secretion. However, the mechanisms responsible for reduced proinsulin processing in the context of SERCA2 deficiency remain incompletely understood. To test this, we developed mice with β cell specific SERCA2 deletion (βS2KO mice) and S2KO INS1 cells. βS2KO mice exhibited age-dependent glucose intolerance and reduced glucose-stimulated insulin secretion without evidence of impaired insulin sensitivity. ER Ca2+ levels in islets from βS2KO mice were significantly reduced, while serum proinsulin/insulin (PI/I) ratios and whole pancreas PI/I content were elevated. Immunoblot analysis of βS2KO islets and S2KO INS-1 cells revealed reduced active forms of the proinsulin processing enzymes, PC1/3, PC2 and CPE. Restoration of SERCA2b via adenoviral transduction in S2KO INS1 cells was sufficient to restore PC1/3 and PC2 maturation and enzyme activity. Brefeldin A treatment in INS1 cells recapitulated the impairments in PC1/3 and PC2 maturation observed in S2KO cells, suggesting a disturbance in protein trafficking between the ER and Golgi. Consistent with this, trafficking assays were performed using a vesicular stomatitis virus G (VSVG) protein construct and revealed a significantly slower rate of VSVG movement from the ER to the Golgi in S2KO INS1 cells. Moreover, pancreas sections from βS2KO mice showed increased co-localization of proinsulin and ProPC2 in the early compartments of the secretory pathway. Taken together, these data suggest that loss of SERCA2 activity and ER Ca2+ loss in the pancreatic β cell leads to impaired proinsulin processing via reduced maturation and trafficking of proinsulin processing enzymes.
Project description:The Golgi is the hub of the eukaryotic secretory pathway, trafficking proteins and lipids, as well as synthesizing complex sugars. Different biosynthetic reactions are associated with different compartments of its complex architecture. Although pre- and post-Golgi trafficking has been much studied, comparatively little is known about intra-Golgi organization. In this study, secretory vesicles and organelles were separated along an electrophoretic gradient at sub-Golgi resolution, presenting snapshots of the changing relative abundance of hundreds of resident and cargo proteins and glycans in transit through the ER, Golgi compartments and post-Golgi compartments. Furthermore, grouped features in migration profiles reveal the dominant intra-Golgi protein trafficking pathways, showing separate routes for cargo and different groups of resident proteins. As few structural characteristics of proteins or sequence motifs have been associated with specific regions of the Golgi stack, we also carried out a comparative analysis of the transmembrane regions of resident proteins associated with the main migratory profiles identifying the presence of charge amino acids adjacent to the transmembrane helix, exoplasmic Ser and Thr content and helix composition as likely contributors to protein sorting mechanisms.
Project description:Epithelial-to-mesenchymal transition (EMT) gives rise to cells with properties similar to cancer stem cells (CSCs) that drive tumor metastasis. Recently, a screening of a large compound library on a breast EMT model has identified salinomycin, a K+/H+ ionophore, as a highly selective drug towards CSCs. We used the same EMT model to show that salinomycin targets Golgi apparatus. We have performed RNA-seq analysis on HMLE-Twist and HMLE-pBp cells (EMT and non-EMT) that were either mock treated or treated for 24h with micro molar concentration (0.2uM) of salinomycin. Salinomycin induced expression of genes enriched by known ER and Golgi stressors.
Project description:Abnormal distribution of cellular cholesterol is associated with numerous diseases, including cardiovascular and neurodegenerative diseases. Regulated transport of cholesterol is critical for maintaining its proper distribution in the cell, yet the underlying mechanisms remain unclear. Here, we show that lipid transfer proteins, namely ORP9, OSBP, and GRAMD1s/Asters (GRAMD1a/GRAMD1b/GRAMD1c), control non-vesicular cholesterol transport at points of contact between the ER and the trans-Golgi network (TGN), thereby maintaining cellular cholesterol distribution. ORP9 localizes to the TGN via interaction between its tandem α-helices and ORP10/ORP11. ORP9 extracts PI4P from the TGN to prevent its overaccumulation and suppresses OSBP-mediated PI4P-driven cholesterol transport to the Golgi. By contrast, GRAMD1s transport excess cholesterol from the Golgi to the ER, thereby preventing its build-up. Cells lacking ORP9 exhibit accumulation of cholesterol at the Golgi, which is further enhanced by additional depletion of GRAMD1s with major accumulation in the plasma membrane. This is accompanied by chronic activation of the SREBP-2 signalling pathway. Our findings reveal the importance of regulated lipid transport at ER-Golgi contacts for maintaining cellular cholesterol distribution and homeostasis.
Project description:Mutations in the IER3IP1 (Immediate early response-3 interacting protein 1) gene can cause MEDS1 (microcephaly with simplified gyral pattern, epilepsy, and permanent neonatal diabetes syndrome-1), a severe disease leading to death in early childhood. The small endoplasmic reticulum-membrane protein IER3IP1 has a non-essential role in ER-Golgi transport. We here use secretome and cell-surface proteomics to show that the loss of IER3IP1 or expression of the pathogenic p.L78P-mutation causes ER retention of selective cell-surface receptors and secreted proteins involved in neuronal migration. This correlates with distension of ER membranes and increased lysosomal activity. Trafficking of the cargo receptor ERGIC53 and of KDEL-receptor 2 are impaired, the latter causing the aberrant secretion of ER-localized chaperones. In utero knock-down of IER3IP1 in brains of mouse embryos displays a morphological phenotype of newborn neurons. Taken together, our data provide hints on how the loss or mutation of a 10 kDa small ER-membrane protein can cause a fatal syndrome.
Project description:To promote infections, pathogens exploit host cell machineries including structural elements of the plasma membrane. Studying these interactions and identifying molecular players is an ideal way to gain insights into the fundamental biology of the host cell. Here, we used the anthrax toxin to screen a library of 1500 regulatory, cell surface, and membrane trafficking genes for their involvement in the intoxication process. We found that ER-Golgi localized proteins TMED2 and TMED10 are required for toxin oligomerization at the plasma-membrane of human cells, an essential step dependant on localization to cholesterol-rich lipid nanodomains. Biochemical, morphological and mechanistic analyses showed that TMED2 and TMED10 are essential components of a complex that operates the exchange of both cholesterol and ceramides at ER-Golgi membrane contact sites. Overall, this study of anthrax intoxication led to the discovery that lipid compositional remodelling at ER-Golgi interfaces fully controls the formation of functional membrane nanodomains at the cell surface.