Figure 4.

The S. cerevisiae CWI (cell wall integrity) pathway: (a) the general flow of information for MAP kinase pathways; (b) schematic diagram of the yeast CWI pathway. The two sensory proteins Mid2 and Wisc1 span the cell wall and are responsible for receiving signals, e.g., heat shock, that are transmitted to the upstream kinase Pkc1 by the mediators Rho1 and Rom2. Pkc1 then activates Bck1 (MAPKKK), which in turn activates Mkk1/Mkk2 (MAPKK), permitting the activation of Slt2 (MAPK). Slt2, in its phosphorylated state, can enter the nucleus, where it influences gene expression by targeting transcription factors, such as the MADS-box transcription factor Rlm1 and the SBF (Swi4/Swi6) transcriptional complex, as well as impacting on polarized growth and processes associated with mitophagy, pexophagy and ER inheritance. Fks2 is an alternative catalytic subunit of the β-1,3-D-glucan synthase whose expression is regulated by cell wall stress and Rho1 [83,84]. The interactions of Prs polypeptides with components of the CWI pathway or their impact thereon, are collated from the following references [64,74,78,79,80,84,92,95,96,97,98,99] and indicated by dashed lines.