Project description:Protein arginine methyltransferases (PRMTs) are a family of enzymes that can methylate arginine residues on histones and other proteins. PRMTs play a crucial role in influencing various cellular functions, including cellular development and tumorigenesis. Arginine methylation by PRMTs is found on both nuclear and cytoplasmic proteins. Recently, there is increasing evidence regarding post-translational modifications of non-histone proteins by PRMTs, illustrating the previously unknown importance of PRMTs in the regulation of various cellular functions by post-translational modifications. In this review, we present the recent developments in the regulation of non-histone proteins by PRMTs.
Project description:BackgroundRods and cones are photoreceptor neurons in the retina that are required for visual sensation in vertebrates, wherein the perception of vision is initiated when these neurons respond to photons in the light stimuli. The photoreceptor cell is structurally studied as outer segments (OS) and inner segments (IS) where proper protein sorting, localization, and compartmentalization are critical for phototransduction, visual function, and survival. In human retinal diseases, improper protein transport to the OS or mislocalization of proteins to the IS and other cellular compartments could lead to impaired visual responses and photoreceptor cell degeneration that ultimately cause loss of visual function.ResultsTherefore, studying and identifying mechanisms involved in facilitating and maintaining proper protein transport in photoreceptor cells would help our understanding of pathologies involving retinal cell degeneration in inherited retinal dystrophies, age-related macular degeneration, and Usher Syndrome.ConclusionsOur mini-review will discuss mechanisms of protein transport within photoreceptors and introduce a novel role for an unconventional motor protein, MYO1C, in actin-based motor transport of the visual chromophore Rhodopsin to the OS, in support of phototransduction and visual function.
Project description:The arrestin clan can now be broadly divided into three structurally similar subgroups: the originally identified arrestins (visual and ?-arrestins), the ?-arrestins and a group of Vps26-related proteins. The visual and ?-arrestins selectively bind to agonist-occupied phosphorylated G protein-coupled receptors (GPCRs) and inhibit GPCR coupling to heterotrimeric G proteins while the ?-arrestins also function as adaptor proteins to regulate GPCR trafficking and G protein-independent signaling. The ?-arrestins have also recently been implicated in regulating GPCR trafficking while Vps26 regulates retrograde trafficking. In this review, we provide an overview of the ?-arrestins and ?-arrestins with a focus on our current understanding of how these adaptor proteins regulate GPCR trafficking.
Project description:Copper is an essential trace element for human biology where its metal dyshomeostasis accounts for an increased level of serum copper, which accelerates protein aggregation. Protein aggregation is a notable feature for many neurodegenerative disorders. Herein, we report an experimental study using two model proteins, bovine serum albumin (BSA) and human serum albumin (HSA), to elucidate the mechanistic pathway by which serum albumins get converted from a fully folded globular protein to a fibril and an amorphous aggregate upon interaction with copper. Steady-state fluorescence, time-resolved fluorescence studies, and Raman spectroscopy were used to monitor the unfolding of serum albumin with increasing copper concentrations. Steady-state fluorescence studies have revealed that the fluorescence quenching of BSA/HSA by Cu(II) has occurred through a static quenching mechanism, and we have evaluated both the quenching constants individually. The binding constants of BSA-Cu(II) and HSA-Cu(II) were found to be 2.42 × 104 and 0.05 × 104 M-1, respectively. Further nanoscale morphological changes of BSA mediated by oligomers to fibril and HSA to amorphous aggregate formation were studied using atomic force microscopy. This aggregation process correlates with the Stern-Volmer plots in the absence of discernible lag phase. Raman spectroscopy results obtained are in good agreement with the increase in antiparallel β-sheet structures formed during the aggregation of BSA in the presence of Cu(II) ions. However, an increase in α-helical fractions is observed for the amorphous aggregate formed from HSA.
Project description:The Hsp70 family of molecular chaperones acts as a central 'hub' in the cell that interacts with numerous newly synthesized proteins to assist in their biogenesis. Apart from its central and well-established role in facilitating protein folding, Hsp70s also act as key decision points in the cellular chaperone network that direct client proteins to distinct biogenesis and quality control pathways. In this paper, we review accumulating data that illustrate a new branch in the Hsp70 network: the post-translational targeting of nascent membrane and organellar proteins to diverse cellular organelles. Work in multiple pathways suggests that Hsp70, via its ability to interact with components of protein targeting and translocation machineries, can initiate elaborate substrate relays in a sophisticated cascade of chaperones, cochaperones, and receptor proteins, and thus provide a mechanism to safeguard and deliver nascent membrane proteins to the correct cellular membrane. We discuss the mechanistic principles gleaned from better-studied Hsp70-dependent targeting pathways and outline the observations and outstanding questions in less well-studied systems.
Project description:During activation of the spliceosome, the U4/U6 snRNA duplex is dissociated, releasing U6 for subsequent base pairing with U2 snRNA. Proteins that directly bind the U4/U6 interaction domain potentially could mediate these structural changes. We thus investigated binding of the human U4/U6-specific proteins, 15.5K, 61K and the 20/60/90K protein complex, to U4/U6 snRNA in vitro. We demonstrate that protein 15.5K is a nucleation factor for U4/U6 snRNP assembly, mediating the interaction of 61K and 20/60/90K with U4/U6 snRNA. A similar hierarchical assembly pathway is observed for the U4atac/U6atac snRNP. In addition, we show that protein 61K directly contacts the 5' portion of U4 snRNA via a novel RNA-binding domain. Furthermore, the 20/60/90K heteromer requires stem II but not stem I of the U4/U6 duplex for binding, and this interaction involves a direct contact between protein 90K and U6. This uneven clustering of the U4/U6 snRNP-specific proteins on U4/U6 snRNA is consistent with a sequential dissociation of the U4/U6 duplex prior to spliceosome catalysis.
Project description:Activator protein-1 (AP-1) regulates a wide range of cellular processes including proliferation, differentiation, and apoptosis. As a transcription factor, AP-1 is commonly found as a heterodimer comprised of c-Jun and c-Fos proteins. However, other heterodimers may also be formed. The function of these dimers, specifically the heterodimeric AP-1 comprised of JunD and c-Fos (AP-1(JunD/c-Fos)), has not been elucidated. Here, we identified a function of AP-1(JunD/c-Fos) in Xenopus hematopoiesis. A gain-of-function study performed by overexpressing junD and c-fos and a loss-of-function study using morpholino junD demonstrate a critical role for AP-1(JunD/c-Fos) in hematopoiesis during Xenopus embryogenesis. Additionally, we confirmed that JunD of AP-1(JunD/c-Fos) is required for BMP-4-induced hematopoiesis. We also demonstrated that BMP-4 regulated JunD activity at the transcriptional regulation and post-translational modification levels. Collectively, our findings identify AP-1(JunD/c-Fos) as a novel hematopoietic transcription factor and the requirement of AP-1(JunD/c-Fos) in BMP-4-induced hematopoiesis during Xenopus hematopoiesis.
Project description:Microarray technology has been successfully used in many biology studies to solve the protein-protein interaction (PPI) prediction computationally. For normal tissue, the cell regulation process begins with transcription and ends with the translation process. However, when cell regulation activity goes wrong, cancer occurs. Microarray data can precisely give high accuracy expression levels at normal and cancer-affected cells, which can be useful for the identification of disease-related genes. First, the differentially expressed genes (DEGs) are extracted from the cancer microarray dataset in order to identify the genes that are up-regulated and down-regulated during cancer progression in the human body. Then, proteins corresponding to these genes are collected from NCBI, and then the STRING web server is used to build the PPI network of these proteins. Interestingly, up-regulated proteins have always a higher number of PPIs compared to down-regulated proteins, although, in most of the datasets, the majority of these DEGs are down-regulated. We hope this study will help to build a relevant model to analyze the process of cancer progression in the human body.
Project description:Age/autoimmune-associated B cells (ABCs) are a T-bet dependent B cell subset, which accumulates prematurely in autoimmune settings. The molecular pathways that regulate ABCs in autoimmunity are largely unknown. The SWEF proteins include SWAP-70 and DEF6, a newly identified SLE risk variant. SWEF-deficient mice (double knock-out=DKO) develop a lupus like syndrome, which is accompanied by a marked expansion of ABCs. The accumulation of ABCs in DKO mice provided us with a unique opportunity to gain new insights into the molecular features that characterize the ABCs that prematurely expand in autoimmune conditions. Splenic Follicular B cells (FoB, B220+CD19+CD23+CD11c-CD11b-) and ABCs (B220+CD19+CD11c+CD11b+) were FACS sorted from >20 weeks old WT or DKO female mice and RNA-seq was employed to compare the transcriptome of DKO ABCs to that of FoB cells derived from either WT or DKO mice. Here we show that loss of SWEF proteins leads to altered gene expression in B cells independently of their differentiation state. In addition, a subset of genes was uniquely regulated in ABCs from DKO mice as compared to FoB cells from either WT or DKO mice. Ananlysis of the ATAC-seq experiment show that the ABCs that expand aberrantly in the DKO autoimmune setting exhibit a unique chromatin landscape and ABC-specific accessible loci displayed enrichment in AP-1/BATF, IRF, and T-bet binding motifs. Together our findings suggest that absence of SWEF proteins affects several key processes in ABCs. In particular, we observed alterations in a number of pathways involved in the control of cellular proliferation and inflammation, a finding that may play a crucial role in the premature accumulation of ABCs in DKOs and could distinguish them from non-autoimmune ABCs.
Project description:Protein S-palmitoylation, a hydrophobic post-translational modification, is performed by protein acyltransferases that have a common DHHC Cys-rich domain (DHHC proteins), and provides a regulatory switch for protein membrane association. In this work, we analyzed the presence of DHHC proteins in the protozoa parasite Giardia lamblia and the function of the reversible S-palmitoylation of proteins during parasite differentiation into cyst. Two specific events were observed: encysting cells displayed a larger amount of palmitoylated proteins, and parasites treated with palmitoylation inhibitors produced a reduced number of mature cysts. With bioinformatics tools, we found nine DHHC proteins, potential protein acyltransferases, in the Giardia proteome. These proteins displayed a conserved structure when compared to different organisms and are distributed in different monophyletic clades. Although all Giardia DHHC proteins were found to be present in trophozoites and encysting cells, these proteins showed a different intracellular localization in trophozoites and seemed to be differently involved in the encystation process when they were overexpressed. dhhc transgenic parasites showed a different pattern of cyst wall protein expression and yielded different amounts of mature cysts when they were induced to encyst. Our findings disclosed some important issues regarding the role of DHHC proteins and palmitoylation during Giardia encystation.