Transduction of centrifugation-induced gravity forces through mitogen-activated protein kinase pathways in the fission yeast Schizosaccharomyces pombe

Centrifugation of cells of Schizosaccharomyces pombe in liquid medium prompted a marked activation of Sty1 and Pmk1, which are the effector mitogen-activated protein kinases (MAPKs) of the stress-activated protein kinase pathway and the cell-integrity pathway, respectively. Transduction of the centrifugation signals showed a sensitivity threshold above which the response was dependent on time and temperature. Centrifugation-induced phosphorylation of Sty1 and Pmk1 required the presence of the main functional components of the respective signalling cascades, i.e. Wak1 or Win1 plus Wis1, and Mkh1 plus Pek1. The transcription factor AM also became phosphorylated in a Sty1-dependent way upon centrifugation. Hypergravity was an important factor in the activation of Sty1 induced by centrifugation, whilst activation of Pmk1 was mostly due to gravity-associated shear forces. Centrifugation did not increase cell survival against other stresses. Rather, the increased gravitational forces produced a delay in the cell cycle, probably related to alterations in the actin-polarization pattern. Phosphorylation of the MAPK Sty1 was needed for the depolarization of actin patches induced by the centrifugation stress.