title: Cooperative autoinhibition and multi-level activation mechanisms of calcineurin.
abstract: The Ca(2+)/calmodulin-dependent protein phosphatase calcineurin (CN), a heterodimer composed of a catalytic subunit A and an essential regulatory subunit B, plays critical functions in various cellular processes such as cardiac hypertrophy and T cell activation. It is the target of the most widely used immunosuppressants for transplantation, tacrolimus (FK506) and cyclosporin A. However, the structure of a large part of the CNA regulatory region remains to be determined, and there has been considerable debate concerning the regulation of CN activity. Here, we report the crystal structure of full-length CN (β isoform), which revealed a novel autoinhibitory segment (AIS) in addition to the well-known autoinhibitory domain (AID). The AIS nestles in a hydrophobic intersubunit groove, which overlaps the recognition site for substrates and immunosuppressant-immunophilin complexes. Indeed, disruption of this AIS interaction results in partial stimulation of CN activity. More importantly, our biochemical studies demonstrate that calmodulin does not remove AID from the active site, but only regulates the orientation of AID with respect to the catalytic core, causing incomplete activation of CN. Our findings challenge the current model for CN activation, and provide a better understanding of molecular mechanisms of CN activity regulation.
authors.affiliation: MOE Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Sheng-Jie
authors.initials: SJ
authors.lastname: Li
authors.affiliation: MOE Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Jue
authors.initials: J
authors.lastname: Wang
authors.affiliation: Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Ma
authors.affiliation: MOE Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Lu
authors.affiliation: MOE Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: MOE Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China.|Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Wu
authors.affiliation: MOE Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China.|Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Zhi-Xin
authors.initials: ZX
authors.lastname: Wang
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000737:chemistry* / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D021122:Protein Subunits / Q000737:chemistry
chemical_list: D002147:Calmodulin; D021122:Protein Subunits; D019703:Calcineurin