Pham C G, Harpf A E, Keller R S, Vu H T, Shai S Y, Loftus J C, Ross R S
Departments of Physiology and Medicine and Cardiovascular Research Laboratories, University of California School of Medicine, Los Angeles, California 90095, USA.
Am J Physiol Heart Circ Physiol. 2000 Dec;279(6):H2916-26. doi: 10.1152/ajpheart.2000.279.6.H2916.
Alterations in the extracellular matrix occur during the cardiac hypertrophic process. Because integrins mediate cell-matrix adhesion and beta(1D)-integrin (beta1D) is expressed exclusively in cardiac and skeletal muscle, we hypothesized that beta1D and focal adhesion kinase (FAK), a proximal integrin-signaling molecule, are involved in cardiac growth. With the use of cultured ventricular myocytes and myocardial tissue, we found the following: 1) beta1D protein expression was upregulated perinatally; 2) alpha(1)-adrenergic stimulation of cardiac myocytes increased beta1D protein levels 350% and altered its cellular distribution; 3) adenovirally mediated overexpression of beta1D stimulated cellular reorganization, increased cell size by 250%, and induced molecular markers of the hypertrophic response; and 4) overexpression of free beta1D cytoplasmic domains inhibited alpha(1)-adrenergic cellular organization and atrial natriuretic factor (ANF) expression. Additionally, FAK was linked to the hypertrophic response as follows: 1) coimmunoprecipitation of beta1D and FAK was detected; 2) FAK overexpression induced ANF-luciferase; 3) rapid and sustained phosphorylation of FAK was induced by alpha(1)-adrenergic stimulation; and 4) blunting of the alpha(1)-adrenergically modulated hypertrophic response was caused by FAK mutants, which alter Grb2 or Src binding, as well as by FAK-related nonkinase, a dominant interfering FAK mutant. We conclude that beta1D and FAK are both components of the hypertrophic response pathway of cardiac myocytes.
细胞外基质的改变发生在心脏肥厚过程中。由于整合素介导细胞与基质的黏附，且β(1D)-整合素（β1D）仅在心肌和骨骼肌中表达，我们推测β1D和黏着斑激酶（FAK）（一种近端整合素信号分子）参与心脏生长。通过使用培养的心室肌细胞和心肌组织，我们发现以下情况：1）β1D蛋白表达在围产期上调；2）α(1)-肾上腺素能刺激心肌细胞可使β1D蛋白水平增加350%并改变其细胞分布；3）腺病毒介导的β1D过表达刺激细胞重组，使细胞大小增加250%，并诱导肥厚反应的分子标志物；4）游离β1D细胞质结构域的过表达抑制α(1)-肾上腺素能细胞组织和心房利钠因子（ANF）表达。此外，FAK与肥厚反应的关系如下：1）检测到β1D和FAK的共免疫沉淀；2）FAK过表达诱导ANF-荧光素酶；3）α(1)-肾上腺素能刺激诱导FAK快速且持续的磷酸化；4）FAK突变体（改变Grb2或Src结合）以及FAK相关非激酶（一种显性干扰性FAK突变体）导致α(1)-肾上腺素能调节的肥厚反应减弱。我们得出结论，β1D和FAK都是心肌细胞肥厚反应途径的组成部分。
