The Function And Mechanism Of SCP1 Dephosphorylation AKT Inhibiting Angiogenesis And Tumorigenesis

Fundamental biological processes are tightly controlled by acute signal transduction pathways.Protein post-translational modification(PTM)which refers to the covalent enzymatic modification,including phosphorylation,ubiquitin,acetylation,methylation,is very essential to regulate various signaling transduction.Protein phosphorylation is one of the most important PTM in the signal transduction.It's well established that phosphorylation can be counterparted by phosphatase to turn off the kinase activity,thereby altering protein function.Knowledge already suggests that there are around 518 protein kinases and about 107 protein phosphatases.Among them,AKT is an essential protein kinase that plays central roles in various cell functions including cell growth,cell migration,tumor progression,angiogenesis and metabolism by phosphorylating kinases and transcription factors.However,how AKT is regulated remains elusive.To search for the potential phosphatases that dephosphorylate AKT,we carried out expression screening strategy with constitutive ly active form of AKT.Our data demonstrate that small C-terminal domain phosphatase 1(SCP1)significantly decreased AKT phosphorylation.Here,we find that gain function of SCP1 dephosphorylates AKT Ser473.In addition,loss of function of SCP1 by shRNA,dramatically increase the Ser473 phosplorylation of AKT,suggesting that SCP1 is indeed negative regulator for AKT.In order to elucidate the in vivo function of Scp1,we successfully generate scp1 KO mice by using CRISPR-CAS9 method.Our data suggest that SCP1 deletion impairs developmental retinal angiogenesis and promotes the recovery of hind limb isochemia compared with wide-type.Then we asked whether function of SCP1 is dependent on AKT activity.To this end,aortic ring assays were performed using in vitro culture of thoracic aorta from Scpl wild type and knockout littermates.Treatment with Akt specific inhibitor can rescue the angiogenesis,indicating that Scpl depletion promotes angiogenic vessels sprout out from aortic ring in an AKT requirement manner.We also examined the effect of Scpl on tumor angiogenesis by irjection of lung cancer cell line LLC into Scpl+/+ or Scpl-/-mouse.Our data show that knockout of Scp1 significantly promoted tumor growth.This is consistence with the assumption that Scpl is aberrantly deregulated in multiple types of human cancers,thus leads to the activation of AKT and consequently promotes cell proliferation and tumorigenesis.Taken together,our results define phosphatase SCP1 is a novel phosphatase for AKT and illustrate that SCP1 function in vivo is dependent on AKT kinase activity.More importantly,our finding may provide mechanistic rationale and new insight into cancer treatment.