6 research outputs found
Myosin 1b and F-actin are involved in the control of secretory granule biogenesis
Hormone secretion relies on secretory granules which store hormones in endocrine cells and release them upon cell stimulation. The molecular events leading to hormone sorting and secretory granule formation at the level of the TGN are still elusive. Our proteomic analysis of purified whole secretory granules or secretory granule membranes uncovered their association with the actomyosin components myosin 1b, actin and the actin nucleation complex Arp2/3. We found that myosin 1b controls the formation of secretory granules and the associated regulated secretion in both neuroendocrine cells and chromogranin A-expressing COS7 cells used as a simplified model of induced secretion. We show that F-actin is also involved in secretory granule biogenesis and that myosin 1b cooperates with Arp2/3 to recruit F-actin to the Golgi region where secretory granules bud. These results provide the first evidence that components of the actomyosin complex promote the biogenesis of secretory granules and thereby regulate hormone sorting and secretion.This work was supported by Institut National de la Santé et de la Recherche Médicale, the University of Rouen Normandy, the Conseil Régional de Normandie and the Ministère de l’Enseignement Supérieur et de la RecherchePeer Reviewe
Secretogranin II is overexpressed in advanced prostate cancer and promotes the neuroendocrine differentiation of prostate cancer cells
Chromogranin A Promotes Peptide Hormone Sorting to Mobile Granules in Constitutively and Regulated Secreting Cells: ROLE OF CONSERVED N- AND C-TERMINAL PEPTIDES*S⃞
Chromogranin A (CgA) has been proposed to play a major role in the
formation of dense-core secretory granules (DCGs) in neuroendocrine cells.
Here, we took advantage of unique features of the frog CgA (fCgA) to assess
the role of this granin and its potential functional determinants in hormone
sorting during DCG biogenesis. Expression of fCgA in the constitutively
secreting COS-7 cells induced the formation of mobile vesicular structures,
which contained cotransfected peptide hormones. The fCgA and the hormones
coexpressed in the newly formed vesicles could be released in a regulated
manner. The N- and C-terminal regions of fCgA, which exhibit remarkable
sequence conservation with their mammalian counterparts were found to be
essential for the formation of the mobile DCG-like structures in COS-7 cells.
Expression of fCgA in the corticotrope AtT20 cells increased
pro-opiomelanocortin levels in DCGs, whereas the expression of N- and
C-terminal deletion mutants provoked retention of the hormone in the Golgi
area. Furthermore, fCgA, but not its truncated forms, promoted
pro-opiomelanocortin sorting to the regulated secretory pathway. These data
demonstrate that CgA has the intrinsic capacity to induce the formation of
mobile secretory granules and to promote the sorting and release of peptide
hormones. The conserved terminal peptides are instrumental for these
activities of CgA
Rare De Novo Missense Variants in RNA Helicase DDX6 Cause Intellectual Disability and Dysmorphic Features and Lead to P-Body Defects and RNA Dysregulation
International audienceThe human RNA helicase DDX6 is an essential component of membrane-less organelles called processing bodies (PBs). PBs are involved in mRNA metabolic processes including translational repression via coordinated storage of mRNAs. Previous studies in human cell lines have implicated altered DDX6 in molecular and cellular dysfunction, but clinical consequences and pathogenesis in humans have yet to be described. Here, we report the identification of five rare de novo missense variants in DDX6 in probands presenting with intellectual disability, developmental delay, and similar dysmorphic features including telecanthus, epicanthus, arched eyebrows, and low-set ears. All five missense variants (p.His372Arg, p.Arg373Gln, p.Cys390Arg, p.Thr391Ile, and p.Thr391Pro) are located in two conserved motifs of the RecA-2 domain of DDX6 involved in RNA binding, helicase activity, and protein-partner binding. We use functional studies to demonstrate that the first variants identified (p.Arg373Gln and p.Cys390Arg) cause significant defects in PB assembly in primary fibroblast and model human cell lines. These variants' interactions with several protein partners were also disrupted in immunoprecipitation assays. Further investigation via complementation assays included the additional variants p.Thr391Ile and p.Thr391Pro, both of which, similarly to p.Arg373Gln and p.Cys390Arg, demonstrated significant defects in P-body assembly. Complementing these molecular findings, modeling of the variants on solved protein structures showed distinct spatial clustering near known protein binding regions. Collectively, our clinical and molecular data describe a neurodevelopmental syndrome associated with pathogenic missense variants in DDX6. Additionally, we suggest DDX6 join the DExD/H-box genes DDX3X and DHX30 in an emerging class of neurodevelopmental disorders involving RNA helicases