TY - JOUR
T1 - (+)Insert smooth muscle myosin heavy chain (SM-B) isoform expression in human tissues
AU - Léguillette, Renaud
AU - Gil, Fulvio R.
AU - Zitouni, Nedjma
AU - Lajoie-Kadoch, Stéphane
AU - Sobieszek, Apolinary
AU - Lauzon, Anne Marie
PY - 2005/11
Y1 - 2005/11
N2 - Two smooth muscle myosin heavy chain isoforms differ in their amino terminus by the presence [(+)insert] or absence [(-)insert] of a seven-amino acid insert. Animal studies show that the (+)insert isoform is predominantly expressed in rapidly contracting phasic muscle and the (-)insert isoform is mostly found in slowly contracting tonic muscle. The expression of the (+)insert isoform has never been demonstrated in human smooth muscle. We hypothesized that the (+)insert isoform is present in humans and that its expression is commensurate with the organ's functional requirements. We report, for the first time, the sequence of the human (+)insert isoform and quantification of its expression by real-time PCR and Western blot analysis in a panel of human organs. The (+)insert isoform mRNA and protein expression levels are significantly greater in small intestine compared with all organs studied except for trachea and are significantly greater in trachea compared with uterus and aorta. To assess the functional significance of this differential myosin isoform expression between organs, we measured the rate of actin filament movement (νmax) when propelled by myosin purified from rat organs, because the rat and human inserts are identical and their remaining sequences show 93% identity. νmax exhibits a rank correlation from the most tonic to the most phasic organ. The selective expression of the (+)insert isoform observed among human organs suggests that it is an important determinant of tissue shortening velocity. A differential expression of the (+)insert isoform could also account for altered contractile properties observed in human pathology.
AB - Two smooth muscle myosin heavy chain isoforms differ in their amino terminus by the presence [(+)insert] or absence [(-)insert] of a seven-amino acid insert. Animal studies show that the (+)insert isoform is predominantly expressed in rapidly contracting phasic muscle and the (-)insert isoform is mostly found in slowly contracting tonic muscle. The expression of the (+)insert isoform has never been demonstrated in human smooth muscle. We hypothesized that the (+)insert isoform is present in humans and that its expression is commensurate with the organ's functional requirements. We report, for the first time, the sequence of the human (+)insert isoform and quantification of its expression by real-time PCR and Western blot analysis in a panel of human organs. The (+)insert isoform mRNA and protein expression levels are significantly greater in small intestine compared with all organs studied except for trachea and are significantly greater in trachea compared with uterus and aorta. To assess the functional significance of this differential myosin isoform expression between organs, we measured the rate of actin filament movement (νmax) when propelled by myosin purified from rat organs, because the rat and human inserts are identical and their remaining sequences show 93% identity. νmax exhibits a rank correlation from the most tonic to the most phasic organ. The selective expression of the (+)insert isoform observed among human organs suggests that it is an important determinant of tissue shortening velocity. A differential expression of the (+)insert isoform could also account for altered contractile properties observed in human pathology.
KW - In vitro motility assay
KW - Phasic and tonic smooth muscle
KW - Real-time polymerase chain reaction
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U2 - 10.1152/ajpcell.00244.2004
DO - 10.1152/ajpcell.00244.2004
M3 - Article
C2 - 16000639
AN - SCOPUS:26844503958
SN - 0363-6143
VL - 289
SP - C1277-C1285
JO - American Journal of Physiology
JF - American Journal of Physiology
IS - 5 58-5
ER -