Post-translationally modified 14-3-3 isoforms and inhibition of protein kinase C

Abstract

This report compares the ability of individual members of the 14-3-3 protein family to inhibit particular protein kinase C (PKC) isoforms. We also show that two of these 14-3-3 isoforms (alpha and delta) specific to mammalian and avian brain are in vivo post-translationally modified forms of beta and zeta respectively. The presence of this modification enhances the activity of 14-3-3 as an inhibitor of protein kinase C nearly two fold. A method for analysing isoforms of 14-3-3 on acid-urea gels is also described. This permits the complete separation of all major isoforms and their unequivocal identification by a range of isoform specific antisera. The activity of recombinant 14-3-3 and isoforms renatured by a novel method after separation by reverse phase HPLC are compared. The effects of diacylglycerol and the phorbol ester, PMA (phorbol 1 2-myristate 13 acetate) on the inhibition suggest that one of the sites of interaction of 14-3-3 may be the cysteine-rich (C1) domain in PKC.

Maintenance of genomic integrity by p53: complementary roles for activated and non-activated p53

“…The 14.3.3-family proteins are found in a wide variety of mammalian tissues and in other eukaryotic organisms including plants and yeast (Aitken et al, 1992), and diverse biochemical properties have been ascribed to them. Mammalian cells contain a minimum of seven 14.3.3 isoforms (Aitken et al, 1995;Wang and Shakes, 1996). Studies in yeast indicate that 14.3.3 proteins have a role in determining the timing of mitosis (Ford et al, 1994).…”

Inhibition of Gap Junction Activity through the Release of the C1B Domain of Protein Kinase Cγ (PKCγ) from 14-3-3

“…Two Zn 2ϩ atoms are coordinated by His and Cys residues at opposite ends of the primary sequence, helping to stabilize the domain. Several reports (26,27) suggest that docking of PKC to 14-3-3 involves the C1B domain of PKC.…”

“…But as reported previously (2,23), PKC␥ will translocate with only a DAG signal. PKCs can bind to a scaffold protein, such as 14-3-3, which is thought to bind in the cytoplasm and can either activate or inhibit an individual PKC isoform (26).…”

Expression of 14-3-3 ζ and interaction with protein kinase C in the rat retina in early diabetes

“…The isotype 1 14-3-3 ζ plays a critical role in neuronal differentiation, synaptic plasticity and exocytosis [1][2][3][4][5][6]23], while PKC activation in diabetes implies diabetes-induced vascular dysfunction [14][15][16]24]. In this study, the molecular levels of 14-3-3 ζ decreased in the retina after 6 weeks of diabetes, while those of PKC β and ζ increased.…”

“…It is well established that 14-3-3 proteins function as a protein kinase C (PKC) regulator [9][10][11][12][13]. In vitro, 14-3-3 ζ has been reported to be an endogenous PKC inhibitor [5,14], but the role of 14-3-3 ζ in the diabetic retina remains unclear.…”