To Explore The Function Of CDK5RAP3 In Mammalian Liver Regeneration

The liver has an unique capacity to regenerate from various types of injuries.The regeneration ability of the liver has important application value for clinical treatment.However,failure of regeneration is frequent in patients with acute liver failure,or after extensive liver resection.Thus,it is important to better understand the mechanism underlying liver homeostasis and regeneration,and identify new therapeutic targets that can control and accelerate liver regeneration.Ubiquitin and ubiquitin-like modification,which are critical post-translation modifications for mammals,are important for liver regeneration.Ubiquitin-fold modifier 1(UFM1)is the most recently identified ubiquitin-like protein.The UFM1 conjugation system consists of UFM1,UBA5(El activating enzyme),UFC1(E2 conjugating enzyme),UFL1(E3 ligase)and UFSPs(UFM1-specific proteases).UFM1 is covalently bound to specific substrate proteins through the tertiary enzyme-linked reaction of E1/E2/E3,and then leads to downstream biological functions.Emerging evidence implicates the Ufmylation is involved in many biology processes including hematopoiesis,brain and liver development,endoplasmic reticulum(ER)stress,fatty acids metabolism and so on.Nonetheless,the role of Ufmylation system in liver regeneration remains largely unclear and merits further investigation.Cdk5rap3 is also known as Lzap and C53.Studies have shown that Cdk5rap3 plays an important role in regulating cell cycle,proliferation,apoptosis,adhesion,invasion and other processes.Besides,CDK5RAP3 has been reported as a substrate of Ufmylation possibly,and has also been found to bind with UFC1,UFL1 and UFBP1.Meanwhile,we found that Cdk5rap3 deficiency in mice led to embryonic lethality at about 16.5-18.5 dpc with significant liver hypoplasia.Liver histology also revealed the deficient hepatocyte with increased apoptosis,and defective differentiation.However,the role and mechanism of Cdk5rap3 in liver regeneration are still unclear and worth further exploring.In our previous works,we detected the in vivo interaction of CDK5RAP3 with UFL1.Notably,loss of CDK5RAP3 altered the Ufmylation profile in liver.We also found Cdk5rap3 deficiency caused ER stress.Thus,we suggested CDK5RAP3 as a UFL1 substrate adaptor,which might play important role in liver regeneration.Here,to investigate the function of CDK5RAP3 in liver regeneration,we generated a hepatocyte-specific Cdk5rap3 knockout(CKO)mouse model by using Alb-Cre transgenic mice.Then,the CKO mice were conducted the standard 70%partial hepatectomy(PH)and then observed the liver regeneration.We found the hepatocytes proliferation was significantly delayed.Meanwhile,CDK5RAP3 deficiency caused increased lipid accumulation and impaired glycogen synthesis and lower blood glucose level after PH.Critically,the absence of CDK5RAP3 seemed to promote inflammatory response and induce apoptosis at late stage of liver regeneration.In addition,CDK5RAP3 deficiency disturbed Ufmylation homeostasis and aggravated ER stress in hepatocytes after PH.Taken together,these results indicate that CDK5RAP3 promotes liver regeneration,at least partially via regulating the cell cycle,glucose and lipid metabolism.Moreover,CDK5RAP3 might be a potential therapeutic target in the treatment of NAFLD patients with aberrant regeneration.