Ouabain interactions with the α4 isoform of the sodium pump trigger non-classical steroid hormone signaling and integrin expression in spermatogenic cells.
In addition to the ubiquitous α1 isoform of the sodium pump, sperm cells also express a male-specific α4 isoform whose function has been associated with sperm motility, fertility, and capacitation. Here we investigate in the murine spermatogenic cell line GC-2 interactions of the α4 isoform with the cardiotonic steroid ouabain in signaling cascades involved in the non-classical action of steroid hormones. Exposure of GC-2 cells to low concentrations of ouabain stimulates the phosphorylation of Erk1/2 and of the transcription factors CREB and ATF-1. As a consequence of this signaling cascade, ouabain stimulates on the mRNA level the expression of integrins αv, β3 and α5, whose expression is also modulated by the cAMP response element. Increased expression of integrins αv and β3 is also seen in cultures of seminiferous tubules exposed to 10nM ouabain. At the protein level we observed a significant stimulation of β3 integrin expression by ouabain. Abrogation of α4 isoform expression by siRNA leads to the complete suppression of all ouabain-induced signaling mentioned above, including its stimulatory effect on the expression of β3 integrin. The results presented here demonstrate for the first time the induction of signaling cascades through the interaction of ouabain with the α4 isoform in a germ-cell derived cell line. The novel finding that these interactions lead to increased expression of integrins in GC-2 cells and the confirmation of these results in the ex vivo experiments indicate that hormone/receptor-like interactions of ouabain with the α4 isoform might be of significance for male physiology.
Institut für Veterinär-Physiologie und -Biochemie, Fachbereich Veterinärmedizin, Justus-Liebig Universität Giessen, Giessen, Germany.
Neha
N
Upmanyu
Institut für Veterinär-Physiologie und -Biochemie, Fachbereich Veterinärmedizin, Justus-Liebig Universität Giessen, Giessen, Germany.
Raimund
R
Dietze
Institut für Veterinär-Physiologie und -Biochemie, Fachbereich Veterinärmedizin, Justus-Liebig Universität Giessen, Giessen, Germany.
Ulrike
U
Kirch
Institut für Veterinär-Physiologie und -Biochemie, Fachbereich Veterinärmedizin, Justus-Liebig Universität Giessen, Giessen, Germany. Electronic address: Georgios.Scheiner-Bobis@vetmed.uni-giessen.de.
Georgios
G
Scheiner-Bobis
D051697:Activating Transcription Factor 1 / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D016023:Integrins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D010042:Ouabain / Q000494:pharmacology*; D010766:Phosphorylation; D034622:RNA Interference; D017208:Rats, Wistar; D012671:Seminiferous Tubules / Q000187:drug effects* / Q000201:enzymology; D015398:Signal Transduction / Q000187:drug effects*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D013094:Spermatozoa / Q000187:drug effects* / Q000201:enzymology; D046509:Tissue Culture Techniques; D014162:Transfection
D051697:Activating Transcription Factor 1; C497100:Atf1 protein, mouse; C492004:Creb1 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D012739:Gonadal Steroid Hormones; D016023:Integrins; D010042:Ouabain; D048049:Extracellular Signal-Regulated MAP Kinases; C401837:Atp1a4 protein, mouse; C485720:Atp1a4 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase
Ouabain; alpha4 isoform; integrin; signaling; sodium pump; spermatogenic cells