Cloning and characterization of the rat Slo3 (K_Ca5.1) channel: From biophysics to pharmacology

Abstract

Background and Purpose: The Slo3 potassium (K Ca 5.1) channel, which is specifically expressed in the testis and sperm, is essential for mammalian male fertilization. The sequence divergence of the bovine, mouse and human Slo3 α-subunit revealed a rapid evolution rate across different species. The rat Slo3 (rSlo3) channel has not been cloned and characterized previously. Experimental Approach: We used molecular cloning, electrophysiology (inside-out patches and outside-out patches) and mutagenesis to investigate the biophysical properties and pharmacological characteristics of the rSlo3 channel.

SLO3: A Conserved Regulator of Sperm Membrane Potential

“…Expression of γ2 depends on SLO3 expression, as Slo3 −/− mice do not express measurable γ2. The primary effect of γ2 is to shift the activation of SLO3 to more negative potentials, as seen in mouse, rat, and human channels [ 69 , 82 , 83 ]. Importantly, mouse SLO3 currents in the presence of γ2 activate at membrane voltage ranges, similar to those of IKSper [ 82 ].…”

“…SLO3 from mice [ 69 , 90 , 91 ], rats [ 83 ], bovines [ 90 ], and humans [ 67 ] is activated by intracellular alkalinization, though the origin of this pH sensitivity is unresolved. Mouse SLO3 channels are more pH-sensitive than bovine channels and contain two histidine residues in the RCK1 domain, whereas bovine channels have only one histidine [ 90 ].…”

“…For example, low concentrations of Ba 2+ have been found to inhibit mouse SLO3 currents [ 24 , 105 , 106 ]. This inhibition also extends to hyperpolarization of CHO cells transfected with human SLO3 and human sperm during capacitation [ 83 ]. Additionally, high concentrations of TEA (Tetraethylammonium) have comparable effects on both human and mouse SLO3 currents [ 83 , 105 , 106 ].…”

“…This inhibition also extends to hyperpolarization of CHO cells transfected with human SLO3 and human sperm during capacitation [ 83 ]. Additionally, high concentrations of TEA (Tetraethylammonium) have comparable effects on both human and mouse SLO3 currents [ 83 , 105 , 106 ]. However, it is important to note that low concentrations of TEA do not hinder human sperm hyperpolarization during capacitation [ 83 ] and have no impact on hKSper currents [ 65 ] or human SLO3 in transfected HEK-293 cells [ 107 ].…”

Two types of peptides derived from the neurotoxin GsMTx4 inhibit a mechanosensitive potassium channel by modifying the mechanogate

“…mSlo1 cDNA was a gift from the laboratory of Dr. Christopher Lingle (Washington University, St. Louis, MO), of which the vector pXMX was designed to promote cRNA expression (12,36,52). pClamp (Molecular Devices) was used to drive stimulus protocols and digitize currents as described previously (51,53). The standard pipette (extracellular) solution contains (in mM): 140 KMES (methanesulfonate), 20 KOH, 10 HEPES, 2 MgCl2, pH 7.0.…”