Abstract
The target of rapamycin complex 2 (TORC2) pathway is evolutionarily conserved and regulates cellular energetics, growth and metabolism. Loss of function of the essential TORC2 subunit Rictor (RICT-1) in Caenorhabditis elegans results in slow developmental rate, reduced brood size, small body size, increased fat mass and truncated lifespan. We performed a rict-1 suppressor RNAi screen of genes encoding proteins that possess the phosphorylation sequence of the AGC family kinase SGK, a key downstream effector of TORC2. Only RNAi to dpy-21 suppressed rict-1 slow developmental rate. DPY-21 functions canonically in the ten-protein dosage compensation complex (DCC) to downregulate the expression of X-linked genes only in hermaphroditic worms. However, we find that dpy-21 functions outside of its canonical role, as RNAi to dpy-21 suppresses TORC2 mutant developmental delay in rict-1 males and hermaphrodites. RNAi to dpy-21 normalized brood size and fat storage phenotypes in rict-1 mutants, but failed to restore normal body size and normal lifespan. Further dissection of the DCC via RNAi revealed that other complex members phenocopy the dpy-21 suppression of rict-1, as did RNAi to the DCC effectors set-1 and set-4, which methylate histone 4 on lysine 20 (H4K20). TORC2/rict-1 animals show dysregulation of H4K20 mono- and tri-methyl silencing epigenetic marks, evidence of altered DCC, SET-1 and SET-4 activity. DPY-21 protein physically interacts with the protein kinase SGK-1, suggesting that TORC2 directly regulates the DCC. Together, the data suggest non-canonical, negative regulation of growth and reproduction by DPY-21 via DCC, SET-1 and SET-4 downstream of TORC2 in C. elegans.
Highlights
The target of rapamycin (TOR) kinase regulates metabolism, development, growth and lifespan by its action in two distinct complexes: TOR complex 1 and TOR complex 2 (Bhaskar and Hay, 2007; Alessi et al, 2009; Jones et al, 2009; Soukas et al, 2009; Lamming et al, 2012)
RESULTS dpy-21 RNA interference (RNAi) suppresses growth delay, reproductive defects and elevated fat mass of the C. elegans TORC2 mutant rict-1 Our previous work shows that mutations in rict-1, a critical subunit of the heteromeric kinase TOR complex 2 (TORC2) in C. elegans, lead to developmental delay (Soukas et al, 2009)
In order to quantify the suppression of rict-1 developmental delay, we studied the developmental timing profile of both wild type and rict1 mutants exposed to dpy-21 RNAi
Summary
The target of rapamycin (TOR) kinase regulates metabolism, development, growth and lifespan by its action in two distinct complexes: TOR complex 1 and TOR complex 2 (Bhaskar and Hay, 2007; Alessi et al, 2009; Jones et al, 2009; Soukas et al, 2009; Lamming et al, 2012). In C. elegans, loss-of-function mutations in the gene encoding the essential TOR complex 2 (TORC2) member RICT-1 leads to small worms with delayed larval development, reduced brood size and shortened lifespan with seemingly inappropriately increased fat stores (Soukas et al, 2009). These phenotypes, with the exception of increased body fat, associated with mutation of TORC2 can be phenocopied by loss of function of the downstream serum and glucocorticoid-induced kinase (SGK1), a protein kinase A, protein kinase G, protein kinase C (AGC) family kinase.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
