In neuroendocrine cells, hormones and neuropeptides are released from large-dense core vesicles (secretory granules) by calcium-regulated exocytosis. Following exocytosis, compensatory uptake of membrane is required to maintain membrane homeostasis and allow recycling of secretory vesicle membranes. How these cells initiate and regulate this compensatory endocytosis remains poorly understood. O...

Electron microscopic studies were made of the parathyroid gland of quail aged 4 to 12 months. Most parenchymal cells consisted of chief cells. Sometimes, cells having numerous microfilaments, scant granular endoplasmic reticulum, a few mitochondria, a small Golgi apparatus, and long cell processes that extended between contiguous cells were located on a basal lamina. These cells may serve as su...

PAT proteins (perilipin, adipophilin, and TIP47) are hypothesized to be critical regulators of lipid accumulation in eukaryotic cells. We investigated the developmental relationships between the expression of these proteins and cytoplasmic lipid droplet (CLD) accumulation in differentiating secretory epithelial cells in mouse mammary glands. Adipophilin (ADPH) specifically localized to CLD in d...

Secretion occurs in all living cells and involves the delivery of intracellular products to the cell exterior. Secretory products are packaged and stored in membranous sacs or vesicles within the cell. When the cell needs to secrete these products, the secretory vesicles containing them dock and fuse at plasma membrane-associated supramolecular structures, called porosomes, to release their con...

The biogenesis, maturation, and exocytosis of secretory granules in interphase cells have been well documented, whereas the distribution and exocytosis of these hormone-storing organelles during cell division have received little attention. By combining ultrastructural analyses and time-lapse microscopy, we here show that, in dividing PC12 cells, the prominent peripheral localization of secreto...

Protease protection assays of apolipoprotein B100 (apoB) in digitonin-permeabilized HepG2 cells indicated that multiple domains of apoB are exposed to the cytosol through an extensive portion of the secretory pathway. The intracellular orientation of apoB in the secretory pathway was confirmed by immunocytochemistry using antibodies recognizing specific domains of apoB in streptolysin-O (STP-O)...

Natural Killer cells are a subset of cytotoxic lymphocytes that are important in host defense against infections and transformed cells. They exert this function through recognition of target cells by cell surface receptors, which triggers a signaling program that results in a re-orientation of the microtubule organizing center and secretory lysosomes toward the target cell. Upon movement of sec...

Murine hepatitis virus (strain A59), (MHV-A59) is a coronavirus that buds into pre-Golgi compartments and then exploits the exocytic pathway of the host cell to reach the exterior. The fibroblastic cells in which replication of this virus is usually studied have only a constitutive exocytic pathway that the virus uses. MHV-A59 also infects, albeit inefficiently, AtT20 cells, murine pituitary tu...

Nerve growth factor-like substance(s) were identified in both conditioned media of a human prostatic tumor epithelial cell line (TSU-pr1) and a human prostatic stromal cell line (HPS) by Western blot analysis and bioassay of neurite outgrowth of PC12 cells. Nerve growth factor-beta (NGF) immunofluorescence was also localized to secretory vesicles in the cytoplasm of both the TSU-pr1 and HPS cel...

Disruption of microtubules has been shown to reduce protein secretion from lactating mammary epithelial cells. To investigate the involvement of microtubules in the secretory pathway in these cells we have examined the effect of nocodazole on protein secretion from mammary epithelial cells derived from the lactating mouse. Mouse mammary cells have extensive microtubule networks and 85% of their...