A genetic variant of the sperm-specific SLO3 K+ channel has altered pH and Ca2+ sensitivities

To fertilize an oocyte, sperm must first undergo capacitation in which the sperm plasma membrane becomes hyperpolarized via activation of potassium (K(+)) channels and resultant K(+) efflux. Sperm-specific SLO3 K(+) channels are responsible for these membrane potential changes critical for fertilization in mouse sperm, and they are only sensitive to pH i However, in human sperm, the major K(+) conductance is both Ca(2+)- and pH i -sensitive. It has been debated whether Ca(2+)-sensitive SLO1 channels substitute for human SLO3 (hSLO3) in human sperm or whether human SLO3 channels have acquired Ca(2+) sensitivity. Here we show that hSLO3 is rapidly evolving and reveal a natural structural variant with enhanced apparent Ca(2+) and pH sensitivities. This variant allele (C382R) alters an amino acid side chain at a principal interface between the intramembrane-gated pore and the cytoplasmic gating ring of the channel. Because the gating ring contains sensors to intracellular factors such as pH and Ca(2+), the effectiveness of transduction between the gating ring and the pore domain appears to be enhanced. Our results suggest that sperm-specific genes can evolve rapidly and that natural genetic variation may have led to a SLO3 variant that differs from wild type in both pH and intracellular Ca(2+) sensitivities. Whether this physiological variation confers differences in fertility among males remains to be established.info:eu-repo/semantics/publishe

The Role of hSLO3 K+ Ion Channel in Sperm Hyperpolarization

Mentor: Larry Salkoff From the Washington University Undergraduate Research Digest: WUURD, Volume 9, Issue 1, Fall 2013. Published by the Office of Undergraduate Research. Joy Zalis Kiefer Director of Undergraduate Research and Assistant Dean in the College of Arts & Sciences

Src is the connecting player between PKA activation and hyperpolarization through SLO3 regulation in mouse sperm

Plasma membrane hyperpolarization is crucial for mammalian sperm to acquire acrosomal responsiveness during capacitation. Among signalling events leading to mammalian sperm capacitation, the immediate activation of protein kinase A plays a pivotal role, promoting the subsequent stimulation of protein tyrosine phosphorylation that associates with fertilizing capacity. We have previously shown that mice deficient on the tyr-kinase cSrc are infertile, and exhibit an improper cauda epididymis development. It is therefore not clear whether lack of sperm functionality is due to problems in epididymal maturation or to the absence of cSrc in sperm. To further address this problem, we investigated the kinetics of cSrc activation using anti phosphor Y416-cSrc antibodies that only recognize active cSrc. Our results provide evidence that cSrc is activated downstream of PKA and that inhibition of its activity blocks the capacitation-induced hyperpolarization of the sperm plasma membrane without blocking the increase in tyrosine phosphorylation that accompany capacitation. In addition, we show that cSrc inhibition also blocked the agonist-induced acrosome reaction and that this inhibition is overcome by pharmacological hyperpolarization. Considering that the capacitation-induced hyperpolarization is mediated by SLO3, we evaluated the action of cSrc inhibitors on heterologously expressed SLO3 channel. Our results indicate that, similarly to SLO1 K+ channels, cSrc blockers decreased significantly SLO3-mediated currents. Altogether these results are consistent with findings that hyperpolarization of the sperm plasma membrane is necessary and sufficient to prepare the sperm for the acrosome reaction and suggest that changes in sperm membrane potential are mediated by cSrc activation.Fil: Stival, Cintia Estefanía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: la Spina, Florenza Antonella. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Baró Graf, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Arcelay, Enid. University of Massachussets; Estados UnidosFil: Arranz, Silvia Eda. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Ferreira, Juan J.. University of Washington. School of Medicine; Estados UnidosFil: Le Grand, Sibylle. University of Washington. School of Medicine; Estados UnidosFil: Dzikunu, Victor A.. University of Washington. School of Medicine; Estados UnidosFil: Santi, Celia M.. University of Washington. School of Medicine; Estados UnidosFil: Visconti, Pablo E.. University of Massachussets; Estados UnidosFil: Buffone, Mariano Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Krapf, Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentin