Wright P S, Lenney C, Carlson D M
Department of Biochemistry and Biophysics, University of California, Davis 95616.
J Mol Endocrinol. 1990 Feb;4(1):81-7. doi: 10.1677/jme.0.0040081.
Proline-rich proteins (PRPs) constitute a group of unusual salivary proteins encoded by tissue-specific multigene families which can be dramatically induced (20- to 70-fold) in vivo in rats, mice and hamsters by treatment with the beta-agonist isoproterenol. Addition of dibutyryl cyclic AMP (dbcAMP) or forskolin to hamster parotid gland primary cultures resulted in a large increase (15- to 30-fold) in PRP mRNA levels. The same time-course and levels of induction of PRP mRNA by dbcAMP and isoproterenol were found in primary cultures, indicating that both effectors act through the same mechanism. Induction by isoproterenol, but not by dbcAMP or forskolin, was blocked by the beta-antagonist propranolol. Incorporation of [3H]proline into PRPs was stimulated in primary cultures by all three effectors. The greatest increase in proline incorporation was in the [3H]PRPs recovered in the culture medium of induced cells. These studies demonstrate that cAMP or agents which increase intracellular cAMP levels increase PRP gene expression in primary cultures of parotid glands. Pretreatment of the cells with cycloheximide blocked the induction of PRP mRNAs which indicates that the synthesis of a trans-acting factor may be necessary for transcriptional activation of the PRP genes. alpha-Amylase mRNA, another tissue-specific gene product, was not significantly affected by cycloheximide treatment.
富含脯氨酸蛋白（PRPs）是一类由组织特异性多基因家族编码的特殊唾液蛋白，在大鼠、小鼠和仓鼠体内，用β-激动剂异丙肾上腺素处理可使其显著诱导（20至70倍）。向仓鼠腮腺原代培养物中添加二丁酰环磷酸腺苷（dbcAMP）或福斯可林，导致PRP mRNA水平大幅增加（15至30倍）。在原代培养物中发现dbcAMP和异丙肾上腺素诱导PRP mRNA的时间进程和水平相同，表明这两种效应物通过相同机制起作用。异丙肾上腺素诱导，但dbcAMP或福斯可林不诱导，可被β-拮抗剂普萘洛尔阻断。所有三种效应物均刺激原代培养物中[3H]脯氨酸掺入PRPs。脯氨酸掺入增加最多的是诱导细胞培养基中回收的[3H]PRPs。这些研究表明，cAMP或增加细胞内cAMP水平的试剂可增加腮腺原代培养物中PRP基因的表达。用环己酰亚胺预处理细胞可阻断PRP mRNA的诱导，这表明反式作用因子的合成可能是PRP基因转录激活所必需的。α-淀粉酶mRNA，另一种组织特异性基因产物，不受环己酰亚胺处理的显著影响。
