Themammaliancalpaingenefamilycurentlycontains13distinctlargesubunitproductsmostofwhichcomplexwithoneoftwosmaller30kDasubunits.(AnexcellentintroductiontotheCalpainfamilycanbefoundonawebsitecreatedbyValeryThompsonhttp://ag.arizona.edu/calpains/index.html)SpreADIngcellsdisplaynewlytransientlyformedintegrinadhesionclusterscontainingCalpain1(mu-Calpain),cleavedTalin,B3-IntegrinandSPTAN1(Spectrin).RecruitmentofRactotheseclustersleadstotheactivationofRacandtheformationofRac-inducedFocalclusters.TheCalpain1intheintegrinclustersinitiallyinactivatesRhoAallowingfortheformationoflamellipodia.ThesubsequentactivationofnewlysynthesizedRhoAtransformstheseclustersintoFocalAdhesionComplexesandtheformationofcontractileactin-myosinstressfibers.Thesematureadhesionsdonotcontaincalpain.

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