Matsuo T, Hazeki K, Tsujimoto N, Inoue S, Kurosu H, Kontani K, Hazeki O, Ui M, Katada T
Ui Laboratory, Institute of Physical and Chemical Research, Wako-shi, Japan.
FEBS Lett. 1996 Nov 11;397(1):113-6. doi: 10.1016/s0014-5793(96)01151-9.
We reported that ecto-NAD+ glycohydrolase activity induced upon differentiation of HL-60 cells with retinoic acid is localized on the extracellular domain of CD38 and that CD38 ligation by a specific monoclonal antibody, HB-7, is followed by rapid tyrosine phosphorylation of cellular proteins including a proto-oncogene product, Cbl. In the present study, we investigated intracellular signaling linked to the HB-7-induced Cbl phosphorylation in dibutyryl cAMP-treated THP-1 cells. The 85-kDa regulatory subunit (p85) of phosphatidylinositol (PI) 3-kinase was immunoprecipitated with anti-Cbl antibody in a manner dependent on the tyrosine phosphorylation of Cbl. PI 3-kinase activity was also observed in the immunoprecipitated fractions containing tyrosine-phosphorylated Cbl. The phosphorylated form of Cbl, which had been separated from the CD38-stimulated cells, was capable of directly binding to a recombinant p85 fused to glutathione S-transferase. Thus, the direct association of tyrosine-phosphorylated Cbl with PI 3-kinase, possibly leading to the kinase activation, appeared to be involved in intracellular signaling caused by the CD38 ligation.
我们曾报道，用视黄酸诱导HL-60细胞分化时所诱导的胞外NAD+糖水解酶活性定位于CD38的胞外结构域，并且用特异性单克隆抗体HB-7连接CD38后，包括原癌基因产物Cbl在内的细胞蛋白会迅速发生酪氨酸磷酸化。在本研究中，我们研究了在二丁酰cAMP处理的THP-1细胞中与HB-7诱导的Cbl磷酸化相关的细胞内信号传导。磷脂酰肌醇（PI）3激酶的85 kDa调节亚基（p85）以依赖于Cbl酪氨酸磷酸化的方式用抗Cbl抗体进行免疫沉淀。在含有酪氨酸磷酸化Cbl的免疫沉淀组分中也观察到PI 3激酶活性。从CD38刺激的细胞中分离出的磷酸化形式的Cbl能够直接与融合了谷胱甘肽S-转移酶的重组p85结合。因此，酪氨酸磷酸化的Cbl与PI 3激酶的直接关联，可能导致激酶激活，似乎参与了由CD38连接引起的细胞内信号传导。
