Regional variation in myosin isoforms and phosphorylation at the resting tone in urinary bladder smooth muscle
Regional variation in myosin isoforms and phosphorylation at the resting tone in urinary bladder smooth muscle
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DOI：
10.1152/ajpcell.2001.280.2.c254
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发表时间：
2001-02-01
影响因子：
5.5
通讯作者：
Chacko, S
中科院分区：
文献类型：
--
作者：
Hypolite, JA;DiSanto, ME;Chacko, S
膀胱充盈和排空需要膀胱体和尿道平滑肌的协调控制。膀胱顶、膀胱中部、膀胱底部和尿道在静息肌肉中20 kDa肌球蛋白轻链（LC 20）磷酸化百分比方面存在显著差异（分别为35.45 +/- 4.6、24.7 +/- 2.2、13.6 +/- 2.1和12.8 +/-2.7%）。激动剂介导的力与LC 20磷酸化的上升，但在所有水平的力的磷酸化程度是小于尿道比膀胱体平滑肌。对膀胱体和尿道平滑肌总RNA的RT-PCR和定量竞争性RT-PCR分析显示，每个总RNA的肌球蛋白重链mRNA拷贝数仅略有差异，而NH 2-末端亚型SM-B的mRNA拷贝数（插入）和SM-A（非插入）在这些肌肉中显示出显着差异（SM-B分别为2.28 x 10（8）vs. 1.68 x 10（8），SM-A分别为0.12 x 10（8）vs. 0.42 x 10（8）），这在蛋白质水平上也很明显。在尿道中的COOH-末端亚型SM 2：SM 1的比例是适度的，但显着低于在膀胱体的其他区域。膀胱体中高度的LC 20磷酸化和SM-B可能有助于促进快速跨桥循环和快速排空所需的力的产生，而尿道平滑肌中较低水平的LC 20磷酸化和较高量的SM-A的存在可能有助于维持尿道的高基础张力，这是排尿所需的。
Urinary bladder filling and emptying requires coordinated control of bladder body and urethral smooth muscles. Bladder dome, midbladder, base, and urethra showed significant differences in the percentage of 20-kDa myosin light chain (LC20) phosphorylation (35.45 +/- 4.6, 24.7 +/- 2.2, 13.6 +/- 2.1, and 12.8 +/- 2.7%, respectively) in resting muscle. Agonist-mediated force was associated with a rise in LC20 phosphorylation, but the extent of phosphorylation at all levels of force was less for urethral than for bladder body smooth muscle. RT-PCR and quantitative competitive RT-PCR analyses of total RNA from bladder body and urethral smooth muscles revealed only a slight difference in myosin heavy chain mRNA copy number per total RNA, whereas mRNA copy numbers for NH2-terminal isoforms SM-B (inserted) and SM-A (noninserted) in these muscles showed a significant difference (2.28 x 10(8) vs. 1.68 x 10(8) for SM-B and 0.12 x 10(8) vs. 0.42 x 10(8) for SM-A, respectively), which was also evident at the protein level. The ratio of COOH-terminal isoforms SM2:SM1 in the urethra was moderately but significantly lower than that in other regions of the bladder body. A high degree of LC20 phosphorylation and SM-B in the bladder body may help to facilitate fast cross-bridge cycling and force generation required for rapid emptying, whereas a lower level of LC20 phosphorylation and the presence of a higher amount of SM-A in urethral smooth muscle may help to maintain the high basal tone of urethra, required for urinary continence.