Pancreatic Beta-Cell Web: Its Possible Role in Insulin Secretion

Abstract

A cortical band of fine microfilaments is consistently observed in the beta cells of the rat pancreas. Alteration of this cell web by cytochalasin B is associated with an enhancement of glucose-induced secretion of insulin by isolated islets. The microfilamentous web of the beta cell may play an important role in the emiocytosis of insulin secretory granules, by controlling their access to the cell membrane.

Both Microtubules and Actin Filaments Are Required for Efficient Postendocytotic Traffic of the Polymeric Immunoglobulin Receptor in Polarized Madin-Darby Canine Kidney Cells

“…We note that recycling of Tf does not require transit through the ARE. In nocodazole-treated cells (in which delivery to the ARE is prevented) (22), Tf recycling occurs with almost identical kinetics to untreated cells (data not shown). The above experiments indicate that a major effect of cytoD treatment was to prevent the efficient translocation of membrane proteins from the basolateral early endosomes to the ARE.…”

Cortical actin recovery at the immunological synapse leads to termination of lytic granule secretion in cytotoxic T lymphocytes

“…Our results suggest that recovered cortical actin may act as a barrier to limit granule secretion during a discrete CTL-target encounter and, furthermore, that recovery itself is triggered upon granule fusion, providing a mechanism that facilitates serial killing during an immune response. We also show that both clearance and recovery of cortical actin occurs concomitantly with complementary changes in PIP 2 , suggesting that The role of actin in secretion has been studied in many cell types specializing in exocytosis, including natural killer (NK) cells (35)(36)(37), mast cells (7), pancreatic β cells (38), and adrenal chromaffin cells (39,40). One model, known as the "barrier model," suggests that the actin cortex acts physically to prevent vesicles from coming in close enough proximity to the plasma membrane for fusion to occur (38).…”

“…We also show that both clearance and recovery of cortical actin occurs concomitantly with complementary changes in PIP 2 , suggesting that The role of actin in secretion has been studied in many cell types specializing in exocytosis, including natural killer (NK) cells (35)(36)(37), mast cells (7), pancreatic β cells (38), and adrenal chromaffin cells (39,40). One model, known as the "barrier model," suggests that the actin cortex acts physically to prevent vesicles from coming in close enough proximity to the plasma membrane for fusion to occur (38). This model is supported by evidence that actin prevents the access of granules and fusion machinery to the plasma membrane in chromaffin cells (41).…”

An in vitro assay reveals a role for the diaphragm protein PV-1 in endothelial fenestra morphogenesis

“…A parallel can be drawn with organelle membrane fusion, where persistence of a surrounding actin coat acts as a physical barrier that prevents the recruitment of tethering factors and, in turn, the close apposition of membranes (40,41). Furthermore, the absence of stress fibers from fenestrated areas appears to be required for their maintenance, given that washout of latrunculin A was followed by a reassembly of actin stress fibers and the disappearance of fenestrae.…”