RECEPTOR AND PROTEIN KINASE-C-MEDIATED REGULATION OF ARF BINDING TO THE GOLGI-COMPLEX

THE formation of constitutive transport vesicles involves the associat ion 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 (A RF) and beta-COP3-5 to Golgi membranes in rat basophilic leukaemia cel ls. Activation of IgE receptors and PKC prevented the ARF and beta-COP dissociation from Golgi membranes that occurs in permeabilized cells in the absence of GTP and potentiated the association-promoting effect s of GTP and the G protein activator fluoroaluminate. In contrast, PKC downregulation and PKC inhibition abolished the activity of GTP and f luoro-luminate in promoting ARF binding to the Golgi complex. Studies of ARF binding to isolated Golgi membranes gave similiar results. Thes e findings suggest that coat assembly on Golgi membranes, and thus pos sibly constitutive secretory traffic, is modulated by membrane recepto rs and second messengers.