A redistribution of actin and myosin IIA accompanies Ca²⁺‐dependent insulin secretion

Abstract

The study addressed the functional link between remodelling of the actomyosin cytoskeleton in pancreatic L L-cells and the regulation of insulin secretion. Confocal microscopy revealed that myosin heavy chain (MHC) IIA co-localized very well with filamentous (F)-actin in RINm5F cells but MHCIIB did not. Subcellular localization of MHCIIB was not altered by stimulation with 30 mM KCl (which evokes Ca 2+ -dependent insulin secretion). In contrast MHCIIA redistributed in a manner similar to F-actin, especially towards the apical surface, but also away from peripheral regions towards cell contact points on the basal surface. Finally, Ca 2+ -dependent insulin secretion was inhibited by stabilization of actin filaments with jasplakinolide. The results support a role for the MHCIIA/actin cytoskeleton in regulating insulin secretion. ß

Cholesterol Regulates Glucose-stimulated Insulin Secretion through Phosphatidylinositol 4,5-Bisphosphate

“…S2). These results are consistent with data showing that actin rearrangement is required for insulin secretion (4,36,37). Together, the data suggest that disruption of membrane microdomains and increased membrane fluidity (Fig.…”

New insights into the control of secretion

“…22 Further, a growing number of recent reports, from a wide range of cell types, are reaching a consensus that F-actin and myosin 2 are dynamic regulators of complex vesicle behavior. Work shows that actin polymerization is triggered immediately after vesicle fusion forming an F-actin network around the vesicle [23][24][25][26][27][28] that keeps the fusion pore open 27 and stabilizes the vesicle shape. 23,24,29,30 In the last year two reports show that myosin 2 phosphorylation directly regulates fusion pore opening.…”

Isoform B of myosin II heavy chain mediates actomyosin contractility during TNFα-induced apoptosis

“…Whereas MHCIIA and MHCIIB share a high degree of homology in the amino-acid sequence (Takahashi et al, 1992), their catalytic activity and intracellular distribution differ (Kawamoto and Adelstein, 1991;Kelley et al, 1996;Lo et al, 2004). This suggests that, although some of the activities of the isoforms overlap (Wylie and Chantler, 2001), intrinsic differences also occur (Kolega, 2003;Lo et al, 2004;Straussman et al, 2001;Swailes et al, 2006;Togo and Steinhardt, 2004;Vicente-Manzanares et al, 2007;Wei and Adelstein, 2000;Wilson et al, 2001;Wylie and Chantler, 2003). In addition, differential phosphorylation of MHCIIs has been shown to be implicated in regulating myosin fiber assembly (Redowicz, 2001).…”