Myosin, smooth muscle heavy chain (SMH)
Myosin is a cytoplasmic actin based motor protein, about 480 kDa, particularly associated with striated muscle cells, smooth muscle cells, and myoepithelial cells. It consist of 2 heavy chains (HC; 223 kDa) and four light chains (LC). Different isotypes of HC are seen in different cell types. In striated muscle cells, HC can be type I = slow myosin, or type II = fast myosin. In smooth muscle cells and myoepithelial cells, there are also two isotypes. Smooth muscle heavy chain myosin (SMH; 200-209 kDa) is a relatively specific marker for terminal smooth muscle cell differentiation, even though myofibroblasts and other cells show limited expression. Thus, SMH has been demonstrated in endothelial cells of lymph node postcapillary venules, splenic sinus lining cells, and dendritic follicular cells in lymph node germinal centres and splenic B-cell areas .
SMH can be demonstrated in the majority of smooth muscle cell tumours and and myoepithelial tumours.
For the identification of smooth muscle cell tumours and and myoepithelial tumours, SMH should be used in a panel of muscle cell markers.
In neoplastic breast lesions, the
myoepithelial cells expressing SMH are usually preserved in
papillomas, benign sclerosing changes and
in situ ductal carcinoma, while not expressed in invasive
clone SMMS-1 is widely used and may give good results both in
concentrated and ready-to-use formats.
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localization of smooth muscle myosin in human spleen, lymph node,
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