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Alternative splicing and cycling kinetics of myosin change during hypertrophy of human smooth muscle cells
Author(s) -
Morano Ingo,
Koehlen Stefan,
Haase Hannelore,
Erb Gunter,
Baltas Leonidas G.,
Rimbach Stephan,
Wallwiener Diethelm,
Bastert Gunther
Publication year - 1997
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(199702)64:2<171::aid-jcb1>3.0.co;2-u
Subject(s) - myometrium , myosin , chemistry , myosin light chain kinase , isometric exercise , endocrinology , medicine , gene isoform , microbiology and biotechnology , biology , biochemistry , uterus , gene
We investigated in vivo expression of myosin heavy chain (MHC) isoforms, 17 kDa myosin light chain (MLC 17 ), and phosphorylation of the 20 kDa MLC (MLC 20 ) as well as mechanical performance of chemically skinned fibers of normal and hypertrophied smooth muscle (SM) of human myometrium. According to their immunological reactivity, we identified three MHC isoenzymes in the human myometrium: two SM‐MHC (SM1 with 204 kDa and SM2 with 200 kDa), and one non‐muscle specific MHC (NM with 196 kDa). No cross‐reactivity was detected with an antibody raised against a peptide corresponding to a seven amino acid insert at the 25K/50K junction of the myosin head (a‐25K/50K) in both normal and hypertrophied myometrium. In contrast, SM‐MHC of human myomatous tissue strongly reacted with a‐25K/50K. Expression of SM1/SM2/NM (%) in normal myometrium was 31.7/34.7/33.6 and 35.1/40.9/24 in hypertrophied myometrium. The increased SM2 and decreased NM expression in the hypertrophied state was statistically significant ( P < 0.05). MHC isoform distribution in myomatous tissue was similar to normal myometrium (35.3/35.3/29.4). In vivo expression of MLC 17a increased from 25.5% in normal to 44.2% in hypertrophied ( P < 0.001) myometrium. Phosphorylation levels of MLC 20 upon maximal Ca 20 ‐calmodulin activation of skinned myometrial fibers were the same in normal and hypertrophied myometrial fibers. Maximal force of isometric contraction of skinned fibers (pCa 4.5, slack‐length) was 2.85 mN/mm 2 and 5.6 mN/mm 2 in the normal and hypertrophied state, respectively ( P < 0.001). Apparent maximal shortening velocity (Vmax app , extrapolated from the force‐velocity relation) of myometrium rose from 0.13 muscle length s 1 (ML/s) in normal to 0.24 ML/s in hypertrophied fibers ( P < 0.001). J. Cell. Biochem, 64:171–181. © 1997 Wiley‐Liss, Inc.