ACTH induces c-fos proto-oncogene in fibroblasts expressing the ACTH receptor

The entire ACTH receptor (ACTH-R) cDNA was amplified by RT/PCR from mouse Y -1 adrenocortical cells, subcloned into the pMOSBlue T vector, sequenced an d inserted into the pSVK3 mammalian vector to obtain pSVACTHR. Balb 3T3 fib roblasts were co-transfected with pSVACTHR plus pSV2-neo and the transfecta nts were selected with G418 and cloned. Genomic integration of pSVACTHR and transcription of ACTH-R cDNA were checked by Southern blot and RT/PCR resp ectively. Expression of active ACTH-R protein was tested by measuring cAMP production in response to ACTH. Two ACTH-R expressing transfectants (clones 03 and 07) increased cAMP accumulation in response to ACTH. They were morp hologically identical to parental 3T3 cells, but required 10-20% FCS to gro w. In these transfectants, ACTH induced c-FOS protein expression, but did n ot activate the ERK isoforms of MAP Kinase and did not stimulate DNA synthe sis. Apparently, the ACTH-R in Balb 3T3 cells induces the c-fos gene by a p athway independent of cAMP/protein kinase A and ERK/MAP Kinase.