Cho-Chung Y S, Clair T, Schwimmer M, Steinberg L, Rego J, Grantham F
Cancer Res. 1981 May;41(5):1840-6.
The molecular species of cyclic adenosine 3':5'-monophosphate (cAMP) receptor proteins (high-affinity-binding proteins) present in hormone-dependent and -independent rat mammary carcinomas were identified and characterized. Three major types of cAMP receptor proteins, with molecular weights of 39,000, 48,000, and 56,000, specifically incorporated the photoaffinity label, 8-azido-cyclic adenosine 3':5'-[32P]monophosphate and were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the tumor cytosols. The M.W. 48,000 and 56,000 receptor proteins appeared to be the regulatory subunits of cAMP-dependent protein kinase types I and II, respectively, and the M.W. 39,000 receptor protein was the proteolytic fragment of the M.W. 56,000 receptor protein. The relative amounts of these cAMP receptor proteins varied from one tumor type to another and showed no correlation with respect to the hormone dependency of tumors. Under two-dimensional gel electrophoresis, however, the M.W. 56,000 receptor protein from hormone-dependent tumors migrated as a doublet and shifted to either a more acidic or more basic charge than that of the receptor protein of hormone-dependent tumors. The alteration of the charge of the receptor did not affect the affinity for cAMP binding, because both hormone-dependent and hormone-independent tumor cytosols exhibited the dissociation constant for cAMP of approximately 10(-8) M. The M.W. 56,000 cAMP receptor protein from hormone-dependent tumors exhibited self-phosphorylation, but that from hormone-independent tumors did not. The diethylaminoethyl cellulose elution profiles of cAMP receptor proteins also differed between hormone-dependent and -independent tumors; cAMP binding activity from hormone-dependent tumors coeluted with cAMP-dependent protein kinase activity, whereas most of the cAMP binding activity from hormone-independent tumors eluted at a higher ionic strength than did cAMP-dependent protein kinase activity. These results suggest that the charge alteration of cAMP receptor proteins, which appears to occur at a site remote from that of cAMP binding, may be associated with the hormone independency of mammary tumors.
对激素依赖性和非依赖性大鼠乳腺癌中存在的环磷酸腺苷（cAMP）受体蛋白（高亲和力结合蛋白）的分子种类进行了鉴定和表征。三种主要类型的cAMP受体蛋白，分子量分别为39,000、48,000和56,000，特异性结合光亲和标记物8-叠氮基环磷酸腺苷3':5'-[32P]单磷酸，并通过肿瘤胞质溶胶的十二烷基硫酸钠-聚丙烯酰胺凝胶电泳进行鉴定。分子量为48,000和56,000的受体蛋白似乎分别是I型和II型cAMP依赖性蛋白激酶的调节亚基，而分子量为39,000的受体蛋白是分子量为56,000的受体蛋白的蛋白水解片段。这些cAMP受体蛋白的相对含量因肿瘤类型而异，与肿瘤的激素依赖性无关。然而，在二维凝胶电泳中，激素依赖性肿瘤中的分子量为56,000的受体蛋白以双峰形式迁移，其电荷比激素依赖性肿瘤的受体蛋白更酸性或更碱性。受体电荷的改变不影响对cAMP结合的亲和力，因为激素依赖性和非依赖性肿瘤胞质溶胶对cAMP的解离常数均约为10(-8) M。激素依赖性肿瘤中分子量为56,000的cAMP受体蛋白表现出自我磷酸化，而非依赖性肿瘤中的则没有。cAMP受体蛋白的二乙氨基乙基纤维素洗脱曲线在激素依赖性和非依赖性肿瘤之间也有所不同；激素依赖性肿瘤的cAMP结合活性与cAMP依赖性蛋白激酶活性共洗脱，而非依赖性肿瘤的大多数cAMP结合活性在比cAMP依赖性蛋白激酶活性更高的离子强度下洗脱。这些结果表明，cAMP受体蛋白的电荷改变似乎发生在远离cAMP结合位点的位置，可能与乳腺肿瘤的激素非依赖性有关。
