| Phosphatase of regenerating liver(PRL)family is classified as class IVa of protein tyrosine phosphatase(PTP4A)that removes phosphate groups from phosphorylated tyrosine residues and serine/threonine residues on proteins.PRLs have been implicated in a number of tumorigenesis and metastasis processes,specially in metastatic and advanced tumors,and is associated with poor prognosis in patients.It is also suggested that PRLs may play a key role in angiogenesis and endothelial cell migration of tumors.However,the pathogenesis of PRLs remain unclear.There are three kinds of PRL in human body,but only one in C.elegans(Caenorhabditis elegans),which provides convenience for studying the mechanism of PRL.Previous studies have found that cPRL is more expressed in L2 and L3 stages of worms,and the longevity of nematodes is significantly prolonged after cPRL RNAi.We attempted to explore the functions of PRL using C.elegans.Through RNAi technology,the level of PRL was reduced in C.elegans by feeding E.coli HT115 expressing dsRNA.As is known that there are three main ways to regulate the lifespan of nematodes,the low insulin-like signaling,the activate SIR-2.1 protein and dietary restrictions.These first two pathways are independent of each other to activate DAF-16 and prolong lifespan.It has been reported that there was no effect on the pharynx pumping by cPRL RNAi,so our study will focuse on the first two pathways.cPRL is more expressed during the L2 and L3 stages,which may regulate the development of nematodes.We first determined the effect of cprl(RNAi)employed from the adult stage and hatching on the lifespan of worms.However,in two of them the effect was non-significant.This observation indicates a longevity supporting effect of cPRL primarily after development in wild-type nematodes.And the cprl-knockdown facilitates the extension of lifespan.Next,we compared the lifespan of daf-2,age-1,akt-1,akt-2,daf-16 and sir-2.1 single mutant animals,respectively,grown on plates with bacteria harboring empty vector or cprl(RNAi).In the experiments,cprl(RNAi)further increased the lifespan of daf-2,age-1,akt-1,akt-2,and sir-2.1 mutants above 10%,except daf-16 mutant.Thus,it appears that the longevity action of cPRL might possess a daf-16 dependent component in wild-type worms.The fact that the impact of cPRL on wild-type lifespan is dependent on DAF-16 suggested a functional link between cPRL and DAF-16.Hence,we asked whether cprl knockdown affects DAF-16 nuclear translocation.We monitored the intracellular localization of DAF-16 in the TJ356 strain containing a daf-16::gfp transgene in response to cprl knockdown employed from hatching.We found that silencing cprl partially promoted the nuclear translocation of DAF-16::GFP during adult.This result indicates reduced cPRL facilitates the activity of pathways regulating DAF-16,which causes DAF-16 to transfer to the nucleus and induces the expression of longevityrelated genes.There are many genes regulated by DAF-16 in the nucleus,including stress resistance related genes.In the heat-shock stress assay,thermal tolerance was significantly increased in the adult worms with cprl-knockdown.However,in the UVirradiation stress assay,the cprl-knockdown worms didnot display longer survival times than the control worms.In conclusion,it was preliminarily determined that the decreased cPRL could prolong the longevity of nematode by transferring DAF-16 to nucleus,and that adult cprl-knockdown worms had the ability to resist heat stress.All of these will further clarify the pathogenic mechanism of PRL in human-related diseases.Moreover,PRL is expected to become treatment target for cancer,and C.elegans can be used as a good model for basic research and targeted drug research of PRL. |
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