Balbaa M
Biochemistry Laboratory, Hokkaido University School of Medicine, Sapporo, Japan.
Hokkaido Igaku Zasshi. 1988 Mar;63(2):277-92.
Previous studies from this laboratory have demonstrated that arylsulfatase B (ASB) is phosphorylated by a protein kinase, which is the first finding of phosphorylation in lysosomal hydrolases. The present study was undertaken to characterize the sites of phosphorylation in ASB from transplanted human lung cancer and from normal human tissues, and to identify type of tumor protein kinase responsible for the phosphorylation of ASB. When ASB purified from liver and placenta was phosphorylated in vitro by a cAMP-dependent protein kinase, it gave a single tryptic phosphopeptide (X) and phosphothreonine. On the other hand, the tumor ASB which had been phosphorylated in vivo demonstrated two phosphopeptides X and Y. Since the tumor ASB had been shown to be phosphorylated both at threonine and serine residues, phosphorylation at threonine residue of peptide X, which is phosphorylated by a cAMP-dependent protein kinase, will be cancer-associated. Through photoaffinity labeling with a labeled cAMP analogue to detect regulatory subunits of cAMP-dependent protein kinase subtypes, it was found that the cAMP-dependent protein kinase in the transplanted lung tumor was largely type II which can be ascribed to the appearance of highly phosphorylated ASB in the tumor.
本实验室之前的研究表明，芳基硫酸酯酶B（ASB）可被一种蛋白激酶磷酸化，这是溶酶体水解酶磷酸化的首次发现。本研究旨在表征移植的人肺癌组织和正常人组织中ASB的磷酸化位点，并鉴定负责ASB磷酸化的肿瘤蛋白激酶类型。当从肝脏和胎盘中纯化的ASB在体外被一种cAMP依赖性蛋白激酶磷酸化时，产生了单一的胰蛋白酶磷酸肽（X）和磷酸苏氨酸。另一方面，在体内已被磷酸化的肿瘤ASB显示出两种磷酸肽X和Y。由于肿瘤ASB已被证明在苏氨酸和丝氨酸残基上均被磷酸化，由cAMP依赖性蛋白激酶磷酸化的肽X的苏氨酸残基上的磷酸化将与癌症相关。通过用标记的cAMP类似物进行光亲和标记以检测cAMP依赖性蛋白激酶亚型的调节亚基，发现移植性肺肿瘤中的cAMP依赖性蛋白激酶主要是II型，这可归因于肿瘤中高度磷酸化的ASB的出现。
