Smooth muscle-type myosin heavy chain isoforms in bovine smooth muscle and non-muscle tissues

Isoforms of the smooth muscle myosin motor, SM1 and SM2, differ in length at the carboxy terminal tail region. Their proportion changes with development, hormonal status and disease, but their function is unknown. We developed mice carrying the myosin heavy chain (MyHC) transgenes SM1, cMyc-tagged SM1, SM2, and V5-tagged SM2, and all transgenes corresponded to the SMa NH2-terminal isoform. Transgene expression was targeted to smooth muscle by the smooth muscle α-actin promoter. Immunoblot analysis showed substantial expression of the cMyc-tagged SM1 and V5-tagged SM2 MyHC protein in aorta and bladder and transgene mRNA was expressed in mice carrying unlabeled SM1 or SM2 transgenes. Despite significant protein expression of tagged MyHCs we found only small changes in the SM1:SM2 protein ratio. Significant changes in functional phenotype were observed in mice carrying unlabeled SM1 or SM2 transgenes. Force in aorta and bladder was increased (72 ± 14%, 92 ± 11%) in SM1 and decreased to 57 ± 1% and 80 ± 3% in SM2 transgenic mice. SM1 transgenic bladders had faster (1.8 ± 0.3 s) and SM2 slower (7.1 ± 0.5 s) rates of force redevelopment following a rapid step shortening. We hypothesize that small changes in the SM1:SM2 ratio could be amplified if they are associated with changes in thick filament assembly and underlie the altered contractility. These data provide evidence indicating an in vivo function for the COOH-terminal isoforms of smooth muscle myosin and suggest that the SM1:SM2 ratio is tightly regulated in smooth muscle tissues.

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CHANGES IN MYOSIN HEAVY CHAIN ISOFORMS AND PROTEINS INVOLVED IN CA2+-SENSITIZATION PATHWAY IN THE DETRUSOR SMOOTH MUSCLE FROM MEN WITH OUTLET OBSTRUCTION INDUCED BY BENIGN PROSTATIC HYPERPLASIA

The Journal of Urology ◽

10.1016/s0022-5347(09)61527-5 ◽

2009 ◽

Vol 181 (4) ◽

pp. 541-542

Author(s):

Jaber A Alanzi ◽

Cristiano M Gomes ◽

Shaohua Chang ◽

S Bruce Malkowicz ◽

Alan J Wein ◽

...

Keyword(s):

Smooth Muscle ◽

Benign Prostatic Hyperplasia ◽

Myosin Heavy Chain ◽

Heavy Chain ◽

Outlet Obstruction ◽

Myosin Heavy Chain Isoforms ◽

Prostatic Hyperplasia ◽

Detrusor Smooth Muscle

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Chronic hypoxia and VEGF differentially modulate abundance and organization of myosin heavy chain isoforms in fetal and adult ovine arteries

AJP Cell Physiology ◽

10.1152/ajpcell.00408.2011 ◽

2012 ◽

Vol 303 (10) ◽

pp. C1090-C1103 ◽

Cited By ~ 19

Author(s):

Margaret C. Hubbell ◽

Andrew J. Semotiuk ◽

Richard B. Thorpe ◽

Olayemi O. Adeoye ◽

Stacy M. Butler ◽

...

Keyword(s):

Smooth Muscle ◽

Myosin Heavy Chain ◽

Heavy Chain ◽

Chronic Hypoxia ◽

Myosin Heavy Chain Isoforms ◽

Wall Structure ◽

Vegf Receptor ◽

Age Dependent ◽

Endothelial Growth Factor

Chronic hypoxia increases vascular endothelial growth factor (VEGF) and thereby promotes angiogenesis. The present study explores the hypothesis that hypoxic increases in VEGF also remodel artery wall structure and contractility through phenotypic transformation of smooth muscle. Pregnant and nonpregnant ewes were maintained at sea level (normoxia) or 3,820 m (hypoxia) for the final 110 days of gestation. Common carotid arteries harvested from term fetal lambs and nonpregnant adults were denuded of endothelium and studied in vitro. Stretch-dependent contractile stresses were 32 and 77% of normoxic values in hypoxic fetal and adult arteries. Hypoxic hypocontractility was coupled with increased abundance of nonmuscle myosin heavy chain (NM-MHC) in fetal (+37%) and adult (+119%) arteries. Conversely, hypoxia decreased smooth muscle MHC (SM-MHC) abundance by 40% in fetal arteries but increased it 123% in adult arteries. Hypoxia decreased colocalization of NM-MHC with smooth muscle α-actin (SM-αA) in fetal arteries and decreased colocalization of SM-MHC with SM-αA in adult arteries. Organ culture with physiological concentrations (3 ng/ml) of VEGF-A165 similarly depressed stretch-dependent stresses to 37 and 49% of control fetal and adult values. The VEGF receptor antagonist vatalanib ablated VEGF's effects in adult but not fetal arteries, suggesting age-dependent VEGF receptor signaling. VEGF replicated hypoxic decreases in colocalization of NM-MHC with SM-αA in fetal arteries and decreases in colocalization of SM-MHC with SM-αA in adult arteries. These results suggest that hypoxic increases in VEGF not only promote angiogenesis but may also help mediate hypoxic arterial remodeling through age-dependent changes in smooth muscle phenotype and contractility.

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Phenotypic Modulation of Smooth Muscle Cells during Progression of Human Atherosclerosis as Determined by Altered Expression of Myosin Heavy Chain Isoforms

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1994.tb17365.x ◽

2006 ◽

Vol 748 (1) ◽

pp. 578-585 ◽

Cited By ~ 20

Author(s):

MASANORI AIKAWA ◽

HYO-SOO KIM ◽

MAKOTO KURO-O ◽

ICHIRO MANABE ◽

MASAFUMI WATANABE ◽

...

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Myosin Heavy Chain ◽

Heavy Chain ◽

Muscle Cells ◽

Myosin Heavy Chain Isoforms ◽

Phenotypic Modulation ◽

Altered Expression ◽

Human Atherosclerosis

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Identification of a novel smooth muscle myosin heavy chain cDNA: isoform diversity in the S1 head region

AJP Cell Physiology ◽

10.1152/ajpcell.1993.264.5.c1252 ◽

1993 ◽

Vol 264 (5) ◽

pp. C1252-C1258 ◽

Cited By ~ 106

Author(s):

S. White ◽

A. F. Martin ◽

M. Periasamy

Keyword(s):

Smooth Muscle ◽

Myosin Heavy Chain ◽

Heavy Chain ◽

Single Gene ◽

Smooth Muscle Myosin ◽

Head Region ◽

Differential Distribution ◽

Isoform Diversity ◽

Muscle Tissues ◽

Muscle Myosin

Smooth muscle myosin heavy chain (SMHC) isoforms, SM1 and SM2, are the products of alternative splicing from a single gene (P. Babij and M. Periasamy. J. Mol. Biol. 210: 673-679, 1989). We have previously shown that this splicing occurs at the 3'-end of the mRNA, resulting in proteins that differ at the carboxyterminal (R. Nagai, M. Kuro-o, P. Babij, and M. Periasamy. J. Biol. Chem. 264: 9734-9737, 1989). In the present study we demonstrate that additional SMHC isoform diversity occurs in the globular head region by isolating and characterizing two distinct rat SMHC cDNA (SMHC-11 = SM1B and SMHC-5 = SM1A). Sequence comparison of the two clones reveals that they are completely identical in their coding regions, except at the region encoding the 25/50 kDa junction of the myosin head, where the SM1B isoform contains an additional seven amino acids. This divergent region is located adjacent to the Mg(2+)-ATPase site, and differences in this region may be of functional importance. Ribonuclease protection analysis demonstrates that the corresponding SM1B and SM1A mRNA messages are coexpressed in all smooth muscle tissues; however, the proportion of the two mRNA present differs significantly between tissues. The SM1A-type mRNA predominates in most smooth muscle tissues, with the exception of intestine and urinary bladder, which contain greater proportions of the SM1B message. The differential distribution of these two isoforms may provide important clues toward understanding differences in smooth muscle contractile properties.

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