Cdc42 activation state affects its localization and protein levels in fission yeast

Abstract

Rho GTPases control polarized cell growth and are well-known regulators of exocytic and endocytic processes. Cdc42 is an essential GTPase, conserved from yeast to humans, that is critical for cell polarization. Cdc42 is negatively regulated by the GTPase-activating proteins (GAPs) and the GDP dissociation inhibitors (GDIs), and positively regulated by guanine nucleotide exchange factors (GEFs). Cdc42 GTPase can be found in a GTP- or GDP-bound state, which determines the ability to bind downstream effector proteins and activate signalling pathways. Only GTP-bound Cdc42 is active. In this study we have analysed the localization of the different nucleotide-bound states of Cdc42 in Schizosaccharomyces pombe: the wild-type Cdc42 protein that cycles between an active and inactive form, the Cdc42G12V form that is permanently bound to GTP and the Cdc42T17N form that is constitutively inactive. Our results indicate that Cdc42 localizes to several membrane compartments in the cell and this localization is mediated by its C-terminal prenylation. Constitutively active Cdc42 localizes mainly to the plasma membrane and concentrates at the growing tips where it is considerably less dynamic than wild-type or GDP-bound Cdc42. Additionally we show that the activation state of Cdc42 also participates in the regulation of its protein levels mediated by endocytosis and by the exocyst complex.

The Multiple Functions of Rho GTPases in Fission Yeasts

“…S. pombe prenylated Cdc42 localizes ubiquitously at the plasma membrane, but it concentrates to the growing cell ends in a GTP-bound (active) form. Polar active Cdc42 is less mobile than the inactive GDP-bound isoform, which localizes primarily to the cell lateral sides (Table 1) (Figure 2A) [56,136,137]. Inhibition of Cdc42 activity at the lateral cortex is achieved by the negative regulation imposed by its GAPs Rga4 and Rga6, and is essential for polarity establishment since GEF-mediated local activation at the cell tips is not enough to restrict Cdc42 activity (Figure 2A) [67,138,139].…”

Spatiotemporal Regulation of Transcript Isoform Expression in the Hippocampus

“…CDC42-prenyl promotes axogenesis in hippocampal neurons (Yap et al, 2016 ). While the role of CDC42-prenyl prenylation in neurons is not yet understood, it may anchor the protein to axons since this modification allows its association with the membrane in S. cerevisiae (Estravís et al, 2017 ). Palmitoylation of CDC42-palm attaches the fatty acid palmitate to either Cys188 or Cys189, which is required for induction of dendritic filopodia, and the development of long protrusions in cultured neurons (Wirth et al, 2013 ).…”

Functional interaction between Cdc42 and the stress MAPK signaling pathway during the regulation of fission yeast polarized growth

“…Fission yeast Cdc42 is an essential GTPase that participates in the establishment and maintenance of cell polarity. It localizes to all cell membranes, but when activated, it concentrates to the plasma membrane of the growth areas (Estravis et al 2011;Bendezu et al 2015;Estravis et al 2017). Cdc42 diffuses laterally in the plasma membrane and accumulates locally as a consequence of the lower mobility of the GTPase in its active form.…”