An AP-3-dependent mechanism drives synaptic-like microvesicle biogenesis in pancreatic islet beta-cells

作者：Suckow Arthur T; Craige Branch; Faundez Victor; Cain William J; Chessler Steven D^*

来源：American Journal of Physiology - Endocrinology And Metabolism, 2010, 299(1): E23-E32.

DOI：10.1152/ajpendo.00664.2009

• adaptin
• beta-cells
• adaptor protein-3
• beta-NAP
• vesicular GABA transporter

Suckow AT, Craige B, Faundez V, Cain WJ, Chessler SD. An AP-3-dependent mechanism drives synaptic-like microvesicle biogenesis in pancreatic islet beta-cells. Am J Physiol Endocrinol Metab 299: E23-E32, 2010. First published May 4, 2010; doi:10.1152/ajpendo.00664.2009.-Pancreaticislet beta-cells contain synaptic-like microvesicles (SLMVs). The origin, trafficking, and role of these SLMVs are poorly understood. In neurons, synaptic vesicle (SV) biogenesis is mediated by two different cytosolic adaptor protein complexes, a ubiquitous AP-2 complex and the neuron-specific AP-3B complex. Mice lacking AP-3B subunits exhibit impaired GABAergic (inhibitory) neurotransmission and reduced neuronal vesicular GABA transporter (VGAT) content. Since beta-cell maturation and exocytotic function seem to parallel that of the inhibitory synapse, we predicted that AP-3B-associated vesicles would be present in beta-cells. Here, we test the hypothesis that AP-3B is expressed in islets and mediates beta-cell SLMV biogenesis. A secondary aim was to test whether the sedimentation properties of INS-1 beta-cell microvesicles are identical to those of bona fide SLMVs isolated from PC12 cells. Our results show that the two neuron-specific AP-3 subunits beta 3B and mu 3B are expressed in beta-cells, the first time these proteins have been found to be expressed outside the nervous system. We found that beta-cell SLMVs share the same sedimentation properties as PC12 SLMVs and contain SV proteins that sort specifically to AP-3B-associated vesicles in the brain. Brefeldin A, a drug that interferes with AP-3-mediated SV biogenesis, inhibits the delivery of AP-3 cargoes to beta-cell SLMVs. Consistent with a role for AP-3 in the biogenesis of GABAergic SLMV in beta-cells, INS-1 cell VGAT content decreases upon inhibition of AP-3 delta-subunit expression. Our findings suggest that beta-cells and neurons share molecules and mechanisms important for mediating the neuron-specific membrane trafficking pathways that underlie synaptic vesicle formation.

• 出版日期2010-7