p21ras farnesyltransferase alpha- and beta-subunits are phosphorylated in PC-12 cells: TGF-beta signaling pathway independent phosphorylation.

Farnesyltransferase (FTase) catalyzes the transfer of a farnesyl isoprenoid to the conserved carboxyl-terminal cysteine residue of proteins terminating with the CAAX sequence. Rat brain FTase is a heterodimer consisting of a 49 kDa alpha-subunit and a 46 kDa beta-subunit. In this report, we show, for the first time, that the beta-subunit of FTase is phosphorylated in vivo and the FTase heterodimer contains phosphorylated alpha/beta-subunits in rat adrenal medulla pheocytochroma PC-12 cells. The presence of the phosphorylated FTase subunits as heterodimer in PC-12 cells which are known to be deficient in TGF-beta signaling pathways argues against the involvement of this pathway in their phosphorylation and heterodimerization.