Modulation of RNA expression by intracellular calcium. Existence of a threshold calcium concentration for induction of VL30 RNA by epidermal growth factor, endothelin, and protein kinase C.
We investigated the role of intracellular [Ca2+] in mediating the independent signal transduction pathways leading to induction of VL30 RNA expression by multiple agonists in the Rat-1-derived RVL-3 cell line. This cell line contains a single integrated VL30 element, and displays a rapid transcriptional activation of VL30 following stimulation by epidermal growth factor, endothelin, or the phorbol ester tumor promoter 12-O-tetradecanoylphorbol acetate (Rodland, K. D., Brown, A. M. C., and Magun, B. E. (1987) M. Cell. Biol. 7, 2296-2298). Neither epidermal growth factor nor endothelin is dependent upon protein kinase C for activation of VL30 expression, as both of these agonists induce normal levels of VL30 RNA expression, even in cells which have been severely depleted of protein kinase C following chronic 12-O-tetradecanoylphorbol acetate exposure. Induction of VL30 RNA expression by either endothelin or 12-O-tetradecanoylphorbol acetate was blocked by concomitant exposure of RVL-3 cells to the intracellular Ca2(+)-chelating agent 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid at a concentration sufficient to buffer intracellular [Ca2+] below 200 nM, and VL30 RNA was induced by the application of the Ca2+ ionophore A23187 in the absence of agonist. Normal levels of VL30 expression in response to epidermal growth factor were observed at 165 nM [Ca2+], but were significantly inhibited at 115 nM [Ca2+]. Both the protein kinase C-dependent and protein kinase C-independent pathways leading to VL30 transcription were dependent upon the presence of an intracellular [Ca2+] exceeding 115 nM. The dependence upon intracellular Ca2+ transients for transcriptional induction by endothelin appears to be a characteristic of VL30 expression, as 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid treatment did not prevent the endothelin-induced transcription of the protooncogenes c-jun and c-fos.
Rodland
K D
KD
Department of Cell Biology and Anatomy, Oregon Health Sciences University, Portland 97201-3098.
Muldoon
L L
LL
Lenormand
P
P
Magun
B E
BE
D000818:Animals; D001572:Benzofurans; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D004533:Egtazic Acid / Q000494:pharmacology / Q000031:analogs & derivatives; D016232:Endothelins; D004730:Endothelium, Vascular; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005456:Fluorescent Dyes; D016257:Fura-2; D007295:Inositol Phosphates / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D019696:Peptidylprolyl Isomerase; D011493:Protein Kinase C / Q000378:metabolism*; D012367:RNA, Viral / Q000096:biosynthesis*; D051381:Rats; D012190:Retroviridae / Q000235:genetics*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic
D001572:Benzofurans; D002352:Carrier Proteins; D016232:Endothelins; D005456:Fluorescent Dyes; D007295:Inositol Phosphates; D010455:Peptides; D012367:RNA, Viral; D000001:Calcimycin; D004533:Egtazic Acid; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D019696:Peptidylprolyl Isomerase; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D016257:Fura-2