title: Loss of SM-B myosin affects muscle shortening velocity and maximal force development.
abstract: We used an exon-specific gene-targeting strategy to generate a mouse model deficient only in the SM-B myosin isoform. Here we show that deletion of exon-5B (specific for SM-B) in the gene for the heavy chain of smooth muscle myosin results in a complete loss of SM-B myosin and switching of splicing to the SM-A isoform, without affecting SM1 and SM2 myosin content. Loss of SM-B myosin does not affect survival or cause any overt smooth muscle pathology. Physiological analysis reveals that absence of SM-B myosin results in a significant decrease in maximal force generation and velocity of shortening in smooth muscle tissues. This is the first in vivo study to demonstrate a functional role for the SM-B myosin isoform. We conclude that the extra seven-residue insert in the surface loop 1 of SM-B myosin is a critical determinant of crossbridge cycling and velocity of shortening.
authors.affiliation: Department of Physiology and Cell Biology, College of Medicine and Public Health, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, Ohio 43210, USA.
authors.forename: G J
authors.initials: GJ
authors.lastname: Babu
authors.forename: E
authors.initials: E
authors.lastname: Loukianov
authors.forename: T
authors.initials: T
authors.lastname: Loukianova
authors.forename: G J
authors.initials: GJ
authors.lastname: Pyne
authors.forename: S
authors.initials: S
authors.lastname: Huke
authors.forename: G
authors.initials: G
authors.lastname: Osol
authors.forename: R B
authors.initials: RB
authors.lastname: Low
authors.forename: R J
authors.initials: RJ
authors.lastname: Paul
authors.forename: M
authors.initials: M
authors.lastname: Periasamy
mesh_terms: D000818:Animals; D005260:Female; D015870:Gene Expression; D006321:Heart / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000378:metabolism / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000502:physiology; D012326:RNA Splicing; D024745:Smooth Muscle Myosins / Q000235:genetics / Q000502:physiology*; D001743:Urinary Bladder / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D024745:Smooth Muscle Myosins