Rkp1/Cpc2, a Fission Yeast rACK1 Homolog, Is Involved in Actin Cytoskeleton Organization through Protein Kinase C, Pck2, Signaling

The Rkp1/Cpc2, a fission yeast RACK1 homolog, interacted with Pck2, one of the known PKC homologs, in vivo and in vitro. The rkp1-deletion mutants (Δrkp1) are elongated and the pck2-deletion mutant (Δpck2) showed abnormal morphology. The double-deletion mutant (Δrkp1Δpck2) showed more aberrant cell shapes and was sensitive to high salt concentration. Both Δrkp1 and Δpck2 cells were sensitive to latrunculin B (Lat B) which inhibits actin polymerization. The cells expressing the human RACK1 homolog complemented the latrunculin B sensitivity of Δrkp1 indicating that human RACK1 is a functional homolog of Rkp1/Cpc2. We propose that Rkp1/Cpc2 may function as a receptor for Pck2 in the regulation of actin cytoskeleton organization during cell wall synthesis and morphogenesis of Schizosaccharomyces pombe.