Distinct vascular and intestinal smooth muscle myosin heavy chain mRNAs are encoded by a single-copy gene in the chicken

Hamada, Y.; Yanagisawa, Masashi; Katsuragawa, Yoshinari; Coleman, John R.; Nagata, Shuichi; Matsuda, Genji; Masaki, Τοmoh

doi:10.1016/0006-291x(90)91239-o

Cited by 72 publications

(39 citation statements)

References 12 publications

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“…Rapidly contracting phasic muscle is predominantly composed of the (ϩ)insert isoform, whereas slowly contracting, tone-maintaining tonic muscle is mostly composed of the (Ϫ)insert isoform (13,46). This pattern of expression suggests that the (ϩ) and (Ϫ)insert isoforms contribute to the different mechanical properties of phasic and tonic muscles.…”

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confidence: 97%

(+)Insert smooth muscle myosin heavy chain (SM-B) isoform expression in human tissues

Léguillette

Gil

Zitouni

et al. 2005

American Journal of Physiology-Cell Physiology

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Animal studies show that the (ϩ)insert isoform is predominantly expressed in rapidly contracting phasic muscle and the (Ϫ)insert isoform is mostly found in slowly contracting tonic muscle. The expression of the (ϩ)insert isoform has never been demonstrated in human smooth muscle. We hypothesized that the (ϩ)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 (ϩ)insert isoform and quantification of its expression by real-time PCR and Western blot analysis in a panel of human organs. The (ϩ)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 ( max) when propelled by myosin purified from rat organs, because the rat and human inserts are identical and their remaining sequences show 93% identity. max exhibits a rank correlation from the most tonic to the most phasic organ. The selective expression of the (ϩ)insert isoform observed among human organs suggests that it is an important determinant of tissue shortening velocity. A differential expression of the (ϩ)insert isoform could also account for altered contractile properties observed in human pathology. phasic and tonic smooth muscle; real-time polymerase chain reaction; in vitro motility assay SMOOTH MUSCLE IS FOUND in all hollow organs of the mammalian organism, and its function ranges from tone maintenance to content propulsion. Many studies point to the smooth muscle myosin heavy chain (SMMHC) as an important element contributing to these diverse contractile properties (see Ref. 16 for review). SMMHC is made up of a globular head, containing an ATPase site and an actin binding domain, and an ␣-helical tail to which regulatory and essential light chains are bound. SMMHC isoforms are generated by alternative splicing from a single gene (1,9,33,46). Four SMMHC isoforms have been described in various animal species. The first two isoforms identified differ in the carboxy terminus by distinct sequences of 43 (SM1) or 9 (SM2) amino acids (2, 33). The next two isoforms differ in the amino terminus by the presence [(ϩ)insert] or absence [(Ϫ)insert] of a seven-amino acid insert in a surface loop above the ATPase site (18, 46). The (ϩ) and (Ϫ)insert isoforms are also commonly referred to as SM-B and SM-A, respectively. All combinations of these isoforms are possible, i.e., (ϩ)insert SM1, (ϩ)insert SM2, (Ϫ)insert SM1, and (Ϫ)insert SM2. No difference in molecular mechanics has been observed between SM1 and SM2, but, as shown with myosin constructs, the sole presence of the amino-terminal insert doubles the actin-activated ATPase activity and the rate of actin filament movement ( max ) in the in vitro motility assay (17,22,36). Because of t...

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confidence: 97%

(+)Insert smooth muscle myosin heavy chain (SM-B) isoform expression in human tissues

Léguillette

Gil

Zitouni

et al. 2005

American Journal of Physiology-Cell Physiology

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“…The expression of these isoforms is tissue specific (1,48). Slowly contracting tonic muscle is mostly composed of the (Ϫ)insert isoform, whereas rapidly contracting phasic muscle predominantly comprises the (ϩ)insert isoform (16,48). Similarly, two isoforms of LC 17 have been reported to have a tissue specific expression, i.e., the acidic isoform LC 17a is mostly expressed in phasic muscle, whereas the basic isoform LC 17b is mostly expressed in tonic muscle (14,31,42).…”

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Smooth muscle myosin isoform expression and LC₂₀phosphorylation in innate rat airway hyperresponsiveness

Gil¹,

Zitouni²,

Maghni³

et al. 2006

American Journal of Physiology-Lung Cellular and Molecular Phys

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Four smooth muscle myosin heavy chain (SMMHC) isoforms are generated by alternative mRNA splicing of a single gene. Two of these isoforms differ by the presence [(ϩ)insert] or absence [(Ϫ)insert] of a 7-amino acid insert in the motor domain. The rate of actin filament propulsion of the (ϩ)insert SMMHC isoform, as measured in the in vitro motility assay, is twofold greater than that of the (Ϫ)insert isoform. We hypothesized that a greater expression of the (ϩ)insert SMMHC isoform and greater regulatory light chain (LC 20) phosphorylation contribute to airway hyperresponsiveness. We measured airway responsiveness to methacholine in Fischer hyperresponsive and Lewis normoresponsive rats and determined SMMHC isoform mRNA and protein expression, as well as essential light chain (LC 17) isoforms, h-caldesmon, and ␣-actin protein expression in their tracheae. We also measured tracheal muscle strip contractility in response to methacholine and corresponding LC 20 phosphorylation. We found Fischer rats have more (ϩ)insert mRNA (69.4 Ϯ 2.0%) (mean Ϯ SE) than Lewis rats (53.0 Ϯ 2.4%; P Ͻ 0.05) and a 44% greater content of (ϩ)insert isoform relative to total myosin protein. No difference was found for LC 17 isoform, h-caldesmon, and ␣-actin expression. The contractility experiments revealed a greater isometric force for Fischer trachealis segments (4.2 Ϯ 0.8 mN) than Lewis (1.9 Ϯ 0.4 mN; P Ͻ 0.05) and greater LC 20 phosphorylation level in Fischer (55.1 Ϯ 6.4) than in Lewis (41.4 Ϯ 6.1; P Ͻ 0.05) rats. These results further support the contention that innate airway hyperresponsiveness is a multifactorial disorder in which increased expression of the fast (ϩ)insert SMMHC isoform and greater activation of LC20 lead to smooth muscle hypercontractility. myosin heavy chain; 7-amino acid insert; phasic muscle; tonic muscle; myosin regulatory light chain; trachealis

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“…Alternate splicing of the 3 Ј end of the MHC gene codes for SM1 and SM2, which differ by 43 amino acids including a 34-amino-acid size difference in the COOH terminal of the myosin molecule (Babij and Periasamy 1989;Nagai et al 1989). Alternate splicing of the 5 Ј end of the gene results in SMA and SMB MHCs, which differ by the presence or absence of a 7-amino-acid insert at the 25-50-kD junction of the myosin molecule (Hamada et al 1990;Kelley et al 1993;White et al 1993). Alternate splicing of a different gene results in LC17a or LC17b, which have the same molecular weight but differ at four of the last nine amino acid positions at the COOH terminus (Nabeshima et al 1987;Lenz et al 1989;Lash et al 1990).…”

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“…Special attention has recently focused on the 25-50-kD junction domain of myosin S1 head, the region of the MHC ATPase site. This is where the seven amino-acid insert resides and appears to be correlated with differences between tonic and phasic contraction (Hamada et al 1990;Kelley et al 1993;Rovner et al 1997;Eddinger and Meer 2001).…”

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Smooth Muscle Myosin Heavy Chain Isoform Distribution in the Swine Stomach

Parisi

Eddinger

2002

J Histochem Cytochem.

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S U M M A R YTo evaluate the distribution of smooth muscle myosin heavy chain isoforms (SMB, with head insert), we examined frozen sections from the various regions of swine stomachs using isoform-specific antibodies. We previously reported variable SMB myosin heavy chain (MHC) expression in stomach cells that correlates with unloaded shortening velocities. This is consistent with the generalization of tonic fundic muscle having low expression and phasic antral muscle having high expression of the SMB MHC isoform. Using immunohistochemistry (IHC), we show a progression of the SMB MHC from very low immunoreactivity in the fundus to very intense immunoreactivity in the antrum. In the body, the average level of SMB MHC immunoreactivity lies between that of the antrum and fundus. Intercellular heterogeneity was observed in all stomach regions to a similar extent. However, the intercellular range in SMB MHC immunoreactivity decreases from fundus to antrum.

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Distinct vascular and intestinal smooth muscle myosin heavy chain mRNAs are encoded by a single-copy gene in the chicken

Cited by 72 publications

References 12 publications

(+)Insert smooth muscle myosin heavy chain (SM-B) isoform expression in human tissues

(+)Insert smooth muscle myosin heavy chain (SM-B) isoform expression in human tissues

Smooth muscle myosin isoform expression and LC₂₀phosphorylation in innate rat airway hyperresponsiveness

Smooth Muscle Myosin Heavy Chain Isoform Distribution in the Swine Stomach

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Distinct vascular and intestinal smooth muscle myosin heavy chain mRNAs are encoded by a single-copy gene in the chicken

Cited by 72 publications

References 12 publications

(+)Insert smooth muscle myosin heavy chain (SM-B) isoform expression in human tissues

(+)Insert smooth muscle myosin heavy chain (SM-B) isoform expression in human tissues

Smooth muscle myosin isoform expression and LC20phosphorylation in innate rat airway hyperresponsiveness

Smooth Muscle Myosin Heavy Chain Isoform Distribution in the Swine Stomach

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Smooth muscle myosin isoform expression and LC₂₀phosphorylation in innate rat airway hyperresponsiveness