Mutations in actin-bundling protein plastin 3(PLS3)emerged as a cause of congenital osteoporosis,but neither the role of PLS3 in bone development nor the mechanisms underlying PLS3-dependent osteoporosis are understoo...Mutations in actin-bundling protein plastin 3(PLS3)emerged as a cause of congenital osteoporosis,but neither the role of PLS3 in bone development nor the mechanisms underlying PLS3-dependent osteoporosis are understood.Of the over 20 identified osteoporosis-linked PLS3 mutations,we investigated all five that are expected to produce full-length protein.One of the mutations distorted an actin-binding loop in the second actin-binding domain of PLS3 and abolished F-actin bundling as revealed by cryo-EM reconstruction and protein interaction assays.Surprisingly,the remaining four mutants fully retained F-actin bundling ability.However,they displayed defects in Ca2+sensitivity:two of the mutants lost the ability to be inhibited by Ca2+;while the other two became hypersensitive to Ca2a.Each group of the mutants with similar biochemical properties showed highly characteristic cellular behavior.Wild-type PLS3 was distributed between lamellipodia and focal adhesions.In striking contrast,the Ca2+-hyposensitive mutants were not found at the leading edge but localized exclusively at focal adhesions/stress fibers,which displayed reinforced morphology.Consistently,the Ca2+-hypersensitive PLS3 mutants were restricted to lamellipodia,while chelation of Ca2+caused their redistribution to focal adhesions.Finally,the bundling-deficient mutant failed to co-localize with any F-actin structures in cells despite a preserved F-actin binding through a non-mutation-bearing actin-binding domain.Our findings revealed that severe osteoporosis can be caused by a mutational disruption of the Ca2+-controlled PLS3’s cycling between adhesion complexes and the leading edge.Integration of the structural,biochemical,and cell biology insights enabled us to propose a molecular mechanism of plastin activity regulation by Ca2+.展开更多
基金This work was supported by the American Cancer Society Institutional Research Grant(to D.S.K.),NIH GM114666(to D.S.K.)and GM122510(to E.H.E.)the Ohio State University Cancer Comprehensive Center Pelotonia Graduate Fellowship(to C.L.S.)Any opinions,findings,and conclusions expressed in this material are those of the authors and do not necessarily reflect those of NIH and the Pelotonia Fellowship Program.
文摘Mutations in actin-bundling protein plastin 3(PLS3)emerged as a cause of congenital osteoporosis,but neither the role of PLS3 in bone development nor the mechanisms underlying PLS3-dependent osteoporosis are understood.Of the over 20 identified osteoporosis-linked PLS3 mutations,we investigated all five that are expected to produce full-length protein.One of the mutations distorted an actin-binding loop in the second actin-binding domain of PLS3 and abolished F-actin bundling as revealed by cryo-EM reconstruction and protein interaction assays.Surprisingly,the remaining four mutants fully retained F-actin bundling ability.However,they displayed defects in Ca2+sensitivity:two of the mutants lost the ability to be inhibited by Ca2+;while the other two became hypersensitive to Ca2a.Each group of the mutants with similar biochemical properties showed highly characteristic cellular behavior.Wild-type PLS3 was distributed between lamellipodia and focal adhesions.In striking contrast,the Ca2+-hyposensitive mutants were not found at the leading edge but localized exclusively at focal adhesions/stress fibers,which displayed reinforced morphology.Consistently,the Ca2+-hypersensitive PLS3 mutants were restricted to lamellipodia,while chelation of Ca2+caused their redistribution to focal adhesions.Finally,the bundling-deficient mutant failed to co-localize with any F-actin structures in cells despite a preserved F-actin binding through a non-mutation-bearing actin-binding domain.Our findings revealed that severe osteoporosis can be caused by a mutational disruption of the Ca2+-controlled PLS3’s cycling between adhesion complexes and the leading edge.Integration of the structural,biochemical,and cell biology insights enabled us to propose a molecular mechanism of plastin activity regulation by Ca2+.
