title: Identification and characterization of Myosin from rat testicular peritubular myoid cells.
abstract: In the mammalian testis, peritubular myoid cells (PMCs) surround seminiferous tubules. These cells are contractile, express the cytoskeletal markers of true smooth muscle-alpha-isoactin and F-actin-and participate in the contraction of seminiferous tubules during the transport of spermatozoa and testicular fluid to the rete testis. Myosin from PMCs (PMC-myosin) was isolated from adult rat testis and purified by cycles of assembly-disassembly and sucrose gradient centrifugation. PMC-myosin was recognized by a monoclonal anti-smooth muscle myosin antibody, and the peptide sequence shared partial homology with rat smooth muscle myosin-II, MYH11 (also known as SMM-II). Most PMC-myosin (95%) was soluble in the PMC cytosol, and purified PMC-myosin did not assemble into filaments in the in vitro salt dialysis assay at 4 degrees C, but did at 20 degrees C. PMC-myosin filaments are stable to ionic strength to the same degree as gizzard MYH11 filaments, but PMC-myosin filaments were more unstable in the presence of ATP. When PMCs were induced to contract by endothelin 1, a fraction of the PMC-myosin was found to be involved in the contraction. From these results we infer that PMCs express an isoform of smooth muscle myosin-II that is characterized by solubility at physiological ionic strength, a requirement for high temperature to assemble into filaments in vitro, and instability at low ATP concentrations. PMC-myosin is part of the PMC contraction apparatus when PMCs are stimulated with endothelin 1.
authors: Laboratory of Cytoskeleton and Cell Cycle, Instituto de Histología y Embriología, Facultad de Ciencias Medicas, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina.
authors: Dario
authors: D
authors: Fernández
authors: Maria V
authors: MV
authors: Bertoldi
authors: Laura
authors: L
authors: Gómez
authors: Alfonsina
authors: A
authors: Morales
authors: Eduardo
authors: E
authors: Callegari
authors: Luis A
authors: LA
authors: Lopez
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002469:Cell Separation; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000096:biosynthesis / Q000737:chemistry*; D010449:Peptide Mapping; D010455:Peptides / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D012671:Seminiferous Tubules / Q000502:physiology; D016622:Silver Staining; D012995:Solubility; D013085:Spermatic Cord / Q000502:physiology; D013737:Testis / Q000166:cytology / Q000378:metabolism*; D014357:Trypsin / Q000737:chemistry; D017539:Tunica Intima / Q000502:physiology
chemical_list: C000595077:Myh11 protein, rat; D010455:Peptides; D000469:Alkaline Phosphatase; D014357:Trypsin; D000251:Adenosine Triphosphatases; D018995:Myosin Heavy Chains