title: T160‐phosphorylated CDK2 defines threshold for HGF dependent proliferation in primary hepatocytes.
abstract: Liver regeneration is a tightly controlled process mainly achieved by proliferation of usually quiescent hepatocytes. The specific molecular mechanisms ensuring cell division only in response to proliferative signals such as hepatocyte growth factor (HGF) are not fully understood. Here, we combined quantitative time-resolved analysis of primary mouse hepatocyte proliferation at the single cell and at the population level with mathematical modeling. We showed that numerous G1/S transition components are activated upon hepatocyte isolation whereas DNA replication only occurs upon additional HGF stimulation. In response to HGF, Cyclin:CDK complex formation was increased, p21 rather than p27 was regulated, and Rb expression was enhanced. Quantification of protein levels at the restriction point showed an excess of CDK2 over CDK4 and limiting amounts of the transcription factor E2F-1. Analysis with our mathematical model revealed that T160 phosphorylation of CDK2 correlated best with growth factor-dependent proliferation, which we validated experimentally on both the population and the single cell level. In conclusion, we identified CDK2 phosphorylation as a gate-keeping mechanism to maintain hepatocyte quiescence in the absence of HGF.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Mueller
authors.forename: Jérémy
authors.initials: J
authors.lastname: Huard
authors.forename: Katharina
authors.initials: K
authors.lastname: Waldow
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Huang
authors.forename: Lorenza A
authors.initials: LA
authors.lastname: D'Alessandro
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bohl
authors.forename: Kathleen
authors.initials: K
authors.lastname: Börner
authors.forename: Dirk
authors.initials: D
authors.lastname: Grimm
authors.forename: Steffen
authors.initials: S
authors.lastname: Klamt
authors.forename: Ursula
authors.initials: U
authors.lastname: Klingmüller
authors.forename: Marcel
authors.initials: M
authors.lastname: Schilling
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D022781:Hepatocytes / Q000187:drug effects*; D008297:Male; D051379:Mice; D008962:Models, Theoretical; D010766:Phosphorylation; D061251:Primary Cell Culture; D059010:Single-Cell Analysis; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D014443:Tyrosine; D017228:Hepatocyte Growth Factor; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2