Eg. Stebbins et D. Mochly-rosen, Binding specificity for RACK1 resides in the V5 region of beta II protein kinase C, J BIOL CHEM, 276(32), 2001, pp. 29644-29650
Identification of selective anchoring proteins responsible for specialized
localization of specific signaling proteins has led to the identification o
f new inhibitors of signal transduction, inhibitors of anchoring protein-li
gand interactions. RACK1, the first receptor for activated C kinase identif
ied in our lab, is a selective anchoring protein for beta II protein kinase
C (beta IIPKC). We previously found that at least part of the RACK1-bindin
g site resides in the C2 domain of beta IIPKC (Ron, D., Luo, J., and Mochly
-Rosen, D. (1995) J. Biol. Chem. 270, 24180-24187). Here we show that the V
5 domain also contains part of the RACK1-binding site in beta IIPKC. In neo
natal rat cardiac myocytes, the beta IIPKC peptide (amino acids 645-650 in
beta IIPKC) selectively inhibited phorbol 12-myristate 13-acetate (PMA)-ind
uced translocation of beta IIPKC and not beta IIPKC. In addition, the beta
IIV5-3 peptide inhibited cardiac myocyte hypertrophy in PMA-treated cells.
Interestingly, beta IV5-3 (646-651 in beta IPKC), a selective translocation
inhibitor of beta IPKC, also inhibited PMA-induced cardiac myocyte hypertr
ophy, demonstrating that both betaI- and beta IIPKC are essential for this
cardiac function. Therefore, the beta IIV5 domain contains part of the RACK
1-binding site in beta IIPKC; a peptide corresponding to this site is a sel
ective inhibitor of beta IIPKC and, hence, enables the identification of be
ta IIPKC-selective functions.