Our earlier work showed that mammalian target of rapamycin (mTOR) is essential 
to the development of various hypertrophic responses, including cardiomyocyte 
survival. mTOR forms two independent complexes, mTORC1 and mTORC2, by 
associating with common and distinct cellular proteins. Both complexes are 
sensitive to a pharmacological inhibitor, torin1, although only mTORC1 is 
inhibited by rapamycin. Since mTORC2 is known to mediate the activation of a 
prosurvival kinase, Akt, we analyzed whether mTORC2 directly mediates Akt 
activation or whether it requires the participation of another prosurvival 
kinase, PKCε (epsilon isoform of protein kinase-C). Our studies reveal that 
treatment of adult feline cardiomyocytes in vitro with insulin results in Akt 
phosphorylation at S473 for its activation which could be augmented with 
rapamycin but blocked by torin1. Silencing the expression of Rictor 
(rapamycin-insensitive companion of mTOR), an mTORC2 component, with a sh-RNA in 
cardiomyocytes lowers both insulin-stimulated Akt and PKCε phosphorylation. 
Furthermore, phosphorylation of PKCε and Akt at the critical S729 and S473 sites 
respectively was blocked by torin1 or Rictor knockdown but not by rapamycin, 
indicating that the phosphorylation at these specific sites occurs downstream of 
mTORC2. Additionally, expression of DN-PKCε significantly lowered the 
insulin-stimulated Akt S473 phosphorylation, indicating an upstream role for 
PKCε in the Akt activation. Biochemical analyses also revealed that PKCε was 
part of Rictor but not Raptor (a binding partner and component of mTORC1). 
Together, these studies demonstrate that mTORC2 mediates prosurvival signaling 
in adult cardiomyocytes where PKCε functions downstream of mTORC2 leading to Akt 
activation.