Nonmuscle myosin II localizes to the Z-lines and intercalated discs of cardiac muscle and to the Z-lines of skeletal muscle.
To understand the role of nonmuscle myosin II in cardiac and skeletal muscle, we used a number of polyclonal antibodies, three detecting nonmuscle myosin heavy chain II-B (NMHC II-B) and two detecting NMHC II-A, to examine the localization of these two proteins in fresh-frozen, acetone-fixed sections of normal human and mouse hearts and human skeletal muscles. Results were similar in both species and were confirmed by examination of fresh-frozen sections of human hearts subjected to no fixation or to treatment with either 4% p-formaldehyde or 50% glycerol. NMHC II-B was diffusely distributed in the cytoplasm of cardiac myocytes during development, but after birth it was localized to the Z-lines and intercalated discs. Dual labeling showed almost complete colocalization of NMHC II-B with alpha-actinin. Whereas endothelial cells, smooth muscle cells and fibroblasts showed strong immunoreactivity for NMHC II-A and NMHC II-B, cardiac myocytes only showed reactivity for the latter. The Z-lines of human skeletal muscle cells, in contrast to those of cardiac myocytes, gave positive reactions for both NMHC II-A and NMHC II-B. The presence of a motor protein in the Z-lines and intercalated discs raises the possibility that these structures may play a more dynamic role in the contraction/relaxation mechanism of cardiac and skeletal muscle than has been previously suspected.
Takeda
K
K
Pathology Section, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Yu
Z X
ZX
Qian
S
S
Chin
T K
TK
Adelstein
R S
RS
Ferrans
V J
VJ
D000185:Actinin / Q000032:analysis / Q000276:immunology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000918:Antibody Specificity; D002648:Child; D002675:Child, Preschool; D003893:Desmin / Q000032:analysis / Q000276:immunology; D005333:Fetus / Q000166:cytology; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes; D006321:Heart / Q000196:embryology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000737:chemistry; D018482:Muscle, Skeletal / Q000737:chemistry* / Q000166:cytology / Q000196:embryology*; D009206:Myocardium / Q000737:chemistry* / Q000166:cytology; D009218:Myosins / Q000032:analysis* / Q000276:immunology; D010590:Phalloidine; D011817:Rabbits; D012235:Rhodamines; D012518:Sarcomeres / Q000737:chemistry; D016707:Tissue Fixation
D003893:Desmin; D005456:Fluorescent Dyes; D012235:Rhodamines; D000185:Actinin; D010590:Phalloidine; D009218:Myosins