Casein kinase 1 controls components of a TORC2 signaling network in budding yeast

Tor kinases play diverse and essential roles in control of nutrient signaling and cell growth. Tor kinases are assembled into two large multiprotein complexes referred to as Tor Complex 1 and Tor Complex 2 (TORC1 and TORC2). In budding yeast, TORC2 controls a signaling network that relays signals regarding carbon source that strongly influence growth rate and cell size. However, the mechanisms that control TORC2 signaling are poorly understood. Activation of TORC2 requires Mss4, a phosphoinositol kinase that initiates assembly of a multi-protein complex at the plasma membrane that recruits and activates downstream targets of TORC2. Localization of Mss4 to the plasma membrane is controlled by phosphorylation and previous work suggested that yeast homologs of casein kinase 1γ, referred to as Yck1 and Yck2, control phosphorylation of Mss4. Here, we generated a new analog-sensitive allele of YCK2 and used it to test whether Yck1/2 influence signaling in the TORC2 network. We found that multiple components of the TORC2 network are strongly influenced by Yck1/2 signaling.