Disease relevance of SM2

• Immunoblotting experiments revealed that antibodies SM1 and SM2 recognize epitopes on two different peptides derived by CNBr cleavage of alpha-pili from Neisseria gonorrhoeae P9-2 [1].
• Expression of SM1 and SM2 MHCs was variable in the different leiomyomas studied [2].
• Reconstituted Sendai virus envelopes containing both the fusion (F) protein and the hemagglutinin-neuraminidase (HN) (F,HN-virosomes) or only the F protein (F-virosomes) were prepared by solubilization of the intact virus with Triton X-100 followed by its removal by using SM2 Bio-Beads [3].
• SMemb expression was increased but SM2 expression was not in the channels of myxoma [4].

High impact information on SM2

• Neointimal SMCs recovered SM MHC expression, first SM1 and then SM2, by 6 months after PTCA [5].
• Smooth muscle myosin heavy chain (SM MHC) isoforms (SM1 and SM2) are specific markers for SMC differentiation [5].
• METHODS AND RESULTS: To determine SMC phenotypes in neointimal tissues after percutaneous transluminal coronary angioplasty (PTCA), we performed immunohistochemistry on human coronary arteries with antibodies against alpha-SM actin, SM1, SM2, and SMemb [5].
• Hydrolysis of membrane-bound SM2 by the recombinant Hex S was synergistically stimulated by the GM2 activator protein and the lysosomal anionic phospholipid bis(monoacylglycero)phosphate [6].
• By double-fluorescence immunostaining of the tunica muscularis of the GI tract wall, co-expression of KIT, CD34, and SMemb was demonstrated in ICCs, which were negative for SM1 and SM2 [7].

Biological context of SM2

• In this study, in order to elucidate any difference in the cellular phenotypes between mesangial cells and renal vascular smooth muscles, we investigated the localization of myosin heavy chain isoforms using a monoclonal antibody against SM1 and SM2 [8].
• Our studies demonstrate that the neural tube influences primary as well as secondary myotube differentiation in avian forelimb and facilitates the expression of different MHC, particularly slow SM2 MHC gene expression in slow myoblasts [9].
• Myosin heavy chain (MHC) isoforms such as SMemb, SM1 and SM2 are important molecular markers used to study vascular smooth muscle cell differentiation [10].
• SM2 was expressed only in the myoepithelial cells of mammary glands in breastfeeding women [11].
• Two myosin heavy chain isoforms expressed in smooth muscle, SM1 (204 kDa) and SM2 (200 kDa), are derived from alternate splicing that results in different amino acid sequences at their non-helical C-terminal tail regions [12].

Anatomical context of SM2

• Both SM1 and SM2 are specific to smooth muscles [8].
• Immunostaining with antibodies against smooth muscle myosins shows that, while SM1 is expressed in all embryonic vessels, SM2 is precociously expressed in the ductus arteriosus [13].
• Recently it was demonstrated that vascular smooth muscles contain two types of myosin heavy chain (MHC) isoforms, SM1 and SM2, which are unique molecular markers of smooth muscle cell phenotypes [14].
• In the KP-MRT-NS cell line, the expression of neurofilament, alpha-smooth-muscle actin, basic calponin and smooth-muscle-myosin heavy chain of SM1 and SM2 isoforms was revealed by immunofluorescence, Western blot and/or reverse transcriptase-polymerase chain reaction (RT-PCR) [15].
• Nevertheless, the expression of slow SM2 isoform in myotubes formed from slow ALD myoblasts only occurred when myoblasts were cultured in the presence of embryonic spinal cord [9].

Associations of SM2 with chemical compounds

• In the abdominal aorta, there were no changes in SM1/SM2 with 17beta-estradiol, and differences in contractility were blunted [16].
• Calcium, phosphorus, lactic acid, and citrate were determined in cheeses made with skim milk (SM2, 3.14% protein), skim milk supplemented with ultrafiltered milk (CSM2, 6.80% protein), and nonfat dry milk (CSM3, 6.80% protein) [17].
• Calcium lactate crystals were observed in cheeses made from SM2 at and below pH 5.1, whereas CLC were observed in cheeses from CSM2 and CSM3 at and below pH 5 [17].
• After 6 days of treatment, SM-2 expression increased, highest in the doxazosin-treated cultures [18].
• RESULTS: The binding assay with 3H-R1881 identified the presence of both cytosolic and nucleosolic androgen receptors in KYN-1/SM10 but not in KYN-1/SM2 [19].

Co-localisations of SM2

• We have shown that an endogenous protease can cleave a small 4 kDa region from the C-terminal of the SM1 isoform which generates a pSM1 species which comigrates with the SM2 isoform on low density SDS gels [20].

Regulatory relationships of SM2

• SM1 is specifically expressed in smooth muscles from early development and SM2 appears after birth [8].
• Predominant SMemb expression indicates presence of phenotypic modulated SMCs and enhanced MMP; while abundant TIMP was seen in mature SMCs expressing SM2 [21].

Other interactions of SM2

• There was a predominance of SM2 isoform mRNA relative to SM1 across all samples, with a mean of 63.8%, which correlated with protein analysis by gel electrophoresis [22].
• The arterial components of AVM contained an abundance of SMCs of the contractile phenotype, which were positive for alpha-actin, SM1 and SM2, but not for SMemb and NMHC-A [23].
• Septal spindle-shaped cells in LC lacked the cytoskeletal proteins specific to differentiated smooth muscle cells (CGA7, SM1, SM2 and desmin) [24].
• Gel electrophoresis and Western blotting, performed with anti-(SM1/SM2 myosin isoform) antibody, indicated quantitative differences between LMS and LM, which mirrored higher positive to negative nuclear ratios for PCNA, Ki67 and apoptosis in malignant as opposed to benign neoplasms [25].
• The expression of the SM2 isoform of smooth muscle myosin heavy chain (SMMHC) mRNA was also examined [26].

Analytical, diagnostic and therapeutic context of SM2

• By immunofluorescence, this signal colocalizes with the expression of the adult-specific smooth muscle myosin heavy chain isoform, SM2 [13].
• In smooth muscle myosin heavy-chain isoforms, SM1 was detected in two parent cell lines composed of S-type cells (MP-N-MS and KP-N-YS) by immunofluorescence, Western blot and/or by RT-PCR, whereas the SM2 isoform was detected in one parent cell line (MP-N-MS) by RT-PCR [27].
• SM-2 to SM-1 mRNA ratios and expression of alpha1-adrenergic receptor subtypes were determined by means of reverse transcriptase polymerase chain reaction (RT-PCR) techniques [18].
• Castration did not suppress the growth of SM2 [28].
• The protein-phospholipid detergent mixtures were then subjected to SM2 Bio-Beads treatments to remove the detergent, and the resulting vesicles were analyzed with respect to protein insertion and orientation in the membrane by freeze-fracture electron microscopy, sucrose density gradients, and proton pumping measurements [29].

References