Modulation of a renal estrogen receptor by protein kinase C

In this paper we demonstrate the existence of specific, high affinity 17-beta estradiol binding in MDBK cells (a normal non-transformed renal cell line). Scatchard analysis revealed binding characteristics typical of the estrogen receptor (ER). Only unlabelled 17-beta estradiol, diethyl stilbestrol and estrone effectively competed with [3H] 17-beta estradiol for binding, other steroids did not compete. Short term TPA treatment of MDBK cells with TPA increased PKC activity and immunoreactivity and caused a transient increase in 17-beta estradiol binding, while longer term treatment with TPA decreased PKC activity and immunoreactivity. The inactive phorbol ester 4 alpha PDD was without effect on PKC activity and the ER. TPA did not affect the affinity of the ER for the nucleus nor did it increase degradation of the receptor. We hypothesize that the renal ER may be a substrate for PKC and its properties can be modified by PKC similarly to the vitamin D receptor.