Yi Xian Ping, Zhou Jibin, Huber Lu, Qu Jiaxiang, Wang Xuejun, Gerdes A Martin, Li Faqian
Cardiovascular Research Institute-South Dakota Health Research Foundation, 1100 East 21st Street, Sioux Falls, SD 57105, USA.
Am J Physiol Heart Circ Physiol. 2006 Jun;290(6):H2509-15. doi: 10.1152/ajpheart.00659.2005. Epub 2005 Dec 22.
Focal adhesion kinase (FAK) and FAK-related non-kinase (FRNK) accumulate in the nucleus of cardiac myocytes during hypertensive hypertrophy. Nuclear FAK and FRNK are phosphorylated on different serines and form distinct bright spots. The subnuclear distribution of serine-phosphorylated FAK and FRNK was examined in this study by double labeling with fibrillarin, a component of nucleoli, and Sam68, a constituent of Sam68 nuclear bodies. We also investigated the role of protein kinase C (PKC)-mediated phosphorylation of FAK and FRNK on nuclear translocation. PKC activation by 12-O-tetradecanoylphorbol 13-acetate treatment increased serine phosphorylation of FAK and FRNK. Specifically, FAK was phosphorylated on serine 722 but not serine 910. On the other hand, FRNK was phosphorylated on serine 217, the equivalent site of FAK serine 910, but not serine 30, the homologous site of FAK serine 722. Serine-phosphorylated FAK and FRNK redistributed into the nucleus and formed distinct patterns. FAK with phosphorylation on serine 722 colocalized with Sam68 but not fibrillarin. On the contrary, FRNK phosphorylated on 217 coexisted with fibrillarin but not Sam68. Immunoprecipitation also confirmed that FAK associated with Sam68 and FRNK interacted with fibrillarin, respectively. These results suggest that FAK and FRNK target different nuclear subdomains by their association with distinct nuclear proteins.
在高血压性心肌肥大过程中，粘着斑激酶（FAK）和FAK相关非激酶（FRNK）在心肌细胞核中积累。核内FAK和FRNK在不同的丝氨酸位点被磷酸化，并形成不同的亮点。本研究通过用核仁成分纤维蛋白原和Sam68核体成分Sam68进行双重标记，检测了丝氨酸磷酸化的FAK和FRNK在细胞核内的分布。我们还研究了蛋白激酶C（PKC）介导的FAK和FRNK磷酸化对核转位的作用。用12 - O - 十四烷酰佛波醇13 - 乙酸酯处理激活PKC，增加了FAK和FRNK的丝氨酸磷酸化。具体而言，FAK在丝氨酸722位点被磷酸化，而丝氨酸910位点未被磷酸化。另一方面，FRNK在丝氨酸217位点被磷酸化，该位点与FAK的丝氨酸910位点等效，而丝氨酸30位点未被磷酸化，该位点与FAK的丝氨酸722位点同源。丝氨酸磷酸化的FAK和FRNK重新分布到细胞核中并形成不同的模式。丝氨酸722位点磷酸化的FAK与Sam68共定位，但不与纤维蛋白原共定位。相反，丝氨酸217位点磷酸化的FRNK与纤维蛋白原共存，但不与Sam68共存。免疫沉淀也证实，FAK与Sam68相互作用，FRNK分别与纤维蛋白原相互作用。这些结果表明，FAK和FRNK通过与不同的核蛋白结合而靶向不同的核亚结构域。
