The Role Of CAMP/PKA Pathway In Cold Tolerance Of Caenorhabditis Elegans

Low environmental temperature can have a significant impact on physiological and behavioural processes in a variety of living organisms,especially for poikilotherms.The mechanisms of cold resistance were reported by previously studies mostly focus on the rebuilt of ion gradients,the production of metabolite and the modification of membrane lipids.However which signalling pathway play a role in poikilothermic to cold stress has not been illuminated.Several studies have shown that the activity of the PKA is increased in wood frogs and some insect at low temperatures.In this study,we also observed the increase of cAMP levels in C.elegans under cold stress.These researchs implicated that the cAMP/PKA pathway may involve in the cold tolerance of poikilotherms.In this research,using a genetically tractable metazoan animal,by genetic means,we found that cAMP-PKA pathway involved in cold stress of C.elegans,which is required for resistance to cold.Our result showed that cold stress activates the cAMP/PKA pathway as well,genetic inactivation of the core components in the cAMP-PKA pathway enhanced the susceptibility of C.elegans to cold stress.Under cold conditions,The lipid content was eventually reduced.To identify which gene(s)is involved in fat mobilization,we screened 29 genes in lipid metabolism pathway,found that only HOSL-1 is involved in fat hydrolysis during cold stress.Meanwhile,cAMP-PKA pathway promotes fat mobilization via up-regulating hosl-1 to resist cold stress.Furthermore,we show that cold stress led to a decrease in water contents in WT worms.And the time of cold treatment is longer,the lost in water contents are more.Another key finding is that the glycerol produced by lipid hydrolysis is beneficial to cold resistance in C.elegans.Exogenous application of glycerol was not only sufficient to restore the resistance to cold stress in kin-1(ok338)mutant or hosl-1 RNAi worms,but also extended the lifespan of WT worms under cold conditions.Our result also proved that in C.elegans,aquaporins are required for response to resistance cold stress in a PKA-dependent manner in C.elegans.Knockdown of aqp-1,aqp-3,and aqp-7,but not other aquaporins,by RNAi led to enhanced sensitivity to cold stress.Finally,under cold condition,PKA in neurons and intestine regulates cold stress.we found that both intestinal-specific knockdown of kin-1 or neuronal RNAi of kin-1 resulted in a decrease in the survival of worms during cold stress.Taken together,the mechanism of cold tolerance in C.elegans is that KIN-1 in the intestine induces the expression of a ligase gene hosl-1,which in turn mediates lipid hydrolysis to produce glycerol.Meanwhile,KIN-1 in the neurons up-regulates the expression of three aquaporins in the intestine,epidermis,and muscles for glycerol transport in a cell-nonautonomous manner,thereby protecting worms against hyperosmotic stress induced by water loss.Our findings provided an example of an evolutionarily conserved mechanism for cold tolerance that has persisted in both poikilothermic and homoeothermic animals.Meanwhile,our work provided a theory for how organisms adapt cold environment and resistance to cold stress.