Stimulation of catecholamine secretion from adrenal chromaffin cells by 14‐3‐3 proteins is due to reorganisation of the cortical actin network

Abstract

Catecholamine release from digitonin-permeabilized adrenal chromaffin cells is increased by exogenous 14--3-3 proteins. In order to determine how 14-3-3 proteins stimulate exocytosis their effect on the cortical actin network was examined. Increased amounts of i~ and 3' isoforms of 14--3-3 proteins were associated with the Triton-insoluble cytoskeleton of chromaffin cells following incubation with exogenous 14-3-3 proteins. The stimulation of catecholamine release by 14-3-3 proteins was abolished by prior incubation with the actin filament stabilising drug phalloidin. Rhodamine phalloidin staining showed that the cortical actin network was disassembled and actin reorganised into intracellular foci following treatment with 14-3-3 proteins. These data suggest that 14-3-3 proteins enhance catecholamine release in permeabilized chromaffin ceils by reorganisation of the cortical actin barrier to allow increased availability of secretory vesicles for exocytosis.

Changes in actin network during calcium-induced exocytosis in permeabilized GH3 cells: calcium directly regulates F-actin disassembly

“…Many agents, such as protein kinase C (Burgoyne et al 1989, Nishizaki et al 1992, calmodulin (Burgoyne 1991, Cheek 1991, fodrin (Burgoyne & Cheek 1987, Perrin et al 1987, gelsolin (Bader et al 1986, Trifaró & Vitale 1993, scinderin (Rodríguez et al 1990, Vitale et al 1995, calpactin , and 14-3-3 proteins (Roth & Burgoyne 1995) and GTP-binding proteins (Norman et al 1994, Price et al 1995, have been studied as Ca 2+ target proteins in the regulation of exocytosis, though the exact mechanisms by which Ca 2+ regulates exocytosis remain unclear. Immunocytochemical studies showed that the cortical actin network was disassembled upon nicotine stimulation of bovine adrenal chromaffin cells (Cheek & Burgoyne 1986, Trifaró & Vitale 1993.…”

“…In the experiments on permeabilized adrenal chromaffin cells, cytochalasins usually potentiated calcium-induced secretion (Lelkes et al 1986, Aunis & Bader 1988, Sontag et al 1988). However, Roth & Burgoyne (1995), who also used digitoninpermeabilized chromaffin cells, reported that cytochalasin had no effect on basal or stimulated catecholamine secretion. We have no reasonable explanation for these differences in the effects of cytochalasin on secretion.…”

Isoform-specific differences in rapid nucleocytoplasmic shuttling cause distinct subcellular distributions of 14-3-3σ and 14-3-3ζ

“…14-3-3s were also found to be associated with membranes Roth et al, 1994;Jones et al, 1995;Tien et al, 1999), the cytoskeleton (Garcia et al, 1999;Ku et al, 1998;Roth and Burgoyne, 1995;Roth et al, 1994) and centrosomes (Pietromonaco et al, 1996). Some reports suggested a specific subcellular distribution for certain isoforms (Roth et al, 1994;Martin et al, 1994;Sehnke et al, 2000;Pietromonaco et al, 1996).…”

Genetic and Electrophysiological Investigation of Learning Memory Mechanisms

“…Likewise, catecholamine release from bovine adrenal chromaffin cells is enhanced by 14-3-3 proteins, which regulate a Ca 2+ -independent, PKC-dependent step of the vesicular trafficking pathway (20-21). 14-3-3 proteins function in this neurosecretory role by mediating the reorganization of the cortical actin cytoskeleton (21), which normally forms a barrier between the vesicles and the plasma membrane. The 14-3-3 protein family is particularly enriched in the mammalian brain (>1% total protein), where these proteins are also thought to be involved in Raf/PKC regulation and vesicular trafficking (2,8).…”