Caenorhabditis elegans hid-1 gene was first identified in a screen for mutants with a high-temperature-induced dauer formation(Hid)phenotype.Despite the fact that the hid-1 gene encodes a novel protein(HID-1)which is highly conserved from Caenorhabditis elegans to mammals,the domain structure,subcellular localization,and exact function of HID-1 remain unknown.Previous studies and various bioinformatic softwares predicted that HID-1 contained many transmembrane domains but no known functional domain.In this study,we revealed that mammalian HID-1 localized to the medial-and transGolgi apparatus as well as the cytosol,and the localization was sensitive to brefeldin A treatment.Next,we demonstrated that HID-1 was a peripheral membrane protein and dynamically shuttled between the Golgi apparatus and the cytosol.Finally,we verified that a conserved N-terminal myristoylation site was required for HID-1 binding to the Golgi apparatus.We propose that HID-1 is probably involved in the intracellular trafficking within the Golgi region.
The molecular mechanisms by which dense core vesicles(DCVs) translocate,tether,dock and prime are poorly understood.In this study,Caenorhabditis elegans was used as a model organism to study the function of Rab proteins and their effectors in DCV exocytosis.RAB-27/AEX-6,but not RAB-3,was found to be required for peptide release from neurons.By analyzing the movement of DCVs approaching the plasma membrane using total internal reflection fluorescence microscopy,we demonstrated that RAB-27/AEX-6 is involved in the tethering of DCVs and that its effector rabphilin/RBF-1 is required for the initial tethering and subsequent stabilization by docking.
FENG Wan JuanLIANG TaoYU JunWeiZHOU WeiZHANG YongDengWU ZhengXingXU Tao
Insulin granule trafficking is a key step in the secretion of glucose-stimulated insulin from pancreaticβ-cells.The main feature of type 2 diabetes(T2D)is the failure of pancreaticβ-cells to secrete sufficient amounts of insulin to maintain normal blood glucose levels.In this work,we developed and applied tomography based on scanning transmission electron microscopy(STEM)to image intact insulin granules in theβ-cells of mouse pancreatic islets.Using three-dimensional(3D)recon-struction,we found decreases in both the number and the grey level of insulin granules in db/db mouse pan-creaticβ-cells.Moreover,insulin granules were closer to the plasma membrane in diabeticβ-cells than in control cells.Thus,3D ultra-structural tomography may provide new insights into the pathology of insulin se-cretion in T2D.
