The signalling mucin Msb2 plays two roles in regulating the response to high temperature. Through its extracellular and cytosolic domains, Msb2 regulates the activity of the CEK pathway (Cek1). Through its extracellular (but not cytosolic domain), Msb2 regulates the PCK pathway (Mkc1). Msb2 also regulates the UPR, potentially through the PKC pathway. Together with the RAS pathway (Ras1), the CEK (Cek1) and PKC (Mkc1) pathways regulate survival and hyphae formation at high temperatures. Ssa1 regulates the CEK and PKC pathways, potentially at the level of the cell wall, through a mechanism that has yet to be elucidated, as indicated by the question mark.