title: Modulation of rhodopsin gene expression and signaling mechanisms evoked by endothelins in goldfish and murine pigment cell lines.
abstract: Endothelins (ETs) and sarafotoxins (SRTXs) belong to a family of vasoconstrictor peptides, which regulate pigment migration and/or production in vertebrate pigment cells. The teleost Carassius auratus erythrophoroma cell line, GEM-81, and Mus musculus B16 melanocytes express rhodopsin, as well as the ET receptors, ETB and ETA, respectively. Both cell lines are photoresponsive, and respond to light with a decreased proliferation rate. For B16, the doubling time of cells kept in 14-h light (14L):10-h darkness (10D) was higher compared to 10L:14D, or to DD. The doubling time of cells kept in 10L:14D was also higher compared to DD. Using real-time PCR, we demonstrated that SRTX S6c (12-h treatment, 100 pM and 1 nM; 24-h treatment, 1 nM) and ET-1 (12-h treatment, 10 and 100 pM; 24- and 48-h treatments, 100 pM) increased rhodopsin mRNA levels in GEM-81 and B16 cells, respectively. This modulation involves protein kinase C (PKC) and the mitogen-activated protein kinase cascade in GEM-81 cells, and phospholipase C, Ca(2+), calmodulin, a Ca(2+)/calmodulin-dependent kinase, and PKC in B16 cells. Cells were kept under constant darkness throughout the gene expression experiments. These results show that rhodopsin mRNA levels can be modulated by SRTXs/ETs in vertebrate pigment cells. It is possible that SRTX S6c binding to the ETB receptors in GEM-81 cells, and ET-1 binding to ETA receptors in B16 melanocytes, although activating diverse intracellular signaling mechanisms, mobilize transcription factors such as c-Fos, c-Jun, c-Myc, and neural retina leucine zipper protein. These activated transcription factors may be involved in the positive regulation of rhodopsin mRNA levels in these cell lines.
authors.affiliation: Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, SP, Brasil.
authors.forename: G J D
authors.initials: GJ
authors.lastname: Lopes
authors.forename: C C
authors.initials: CC
authors.lastname: Góis
authors.forename: L H R G
authors.initials: LH
authors.lastname: Lima
authors.forename: A M L
authors.initials: AM
authors.lastname: Castrucci
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects*; D016232:Endothelins / Q000494:pharmacology*; D005786:Gene Expression Regulation; D006054:Goldfish; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D051379:Mice; D016133:Polymerase Chain Reaction; D011493:Protein Kinase C / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D012243:Rhodopsin / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014757:Viper Venoms / Q000494:pharmacology*
chemical_list: D016232:Endothelins; D012333:RNA, Messenger; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6; D012243:Rhodopsin; D011493:Protein Kinase C