Receptor and protein kinase C-mediated regulation of ARF binding to the Golgi complex

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Abstract
THE formation of constitutive transport vesicles involves the association of non-clathrin coat proteins to transport organelles1,2. Here we report that IgE receptors and protein kinase C (PKC) regulate the GTP-dependent binding of the two coat proteins ADP-ribosylation factor (ARF) and β-COP3–5 to Golgi membranes in rat basophilic leukaemia cells. Activation of IgE receptors and PKC prevented the ARF and β-COP dissociation from Golgi membranes that occurs in permeabilized cells in the absence of GTP and potentiated the association-promoting effects of GTP and the G protein activator fluoroluminate. In contrast, PKC downregulation and PKC inhibition abolished the activity of GTP and fluoroluminate in promoting ARF binding to the Golgi complex. Studies of ARF binding to isolated Golgi membranes gave similar results. These findings suggest that coat assembly on Golgi membranes, and thus possibly constitutive secretory traffic, is modulated by membrane receptors and second messengers.