Molecular expression and functional features of Kv7 channels in human prostate smooth muscle

Abstract

Background: Relaxation of prostate smooth muscle tone is a key strategy for the medical treatment of lower urinary tract symptoms (LUTS) in men. However, potassium channel's physiological role inhuman prostatic smooth muscle (HPrSM) has yet to be determined.

Objectives: In this study, we examined the molecular characteristics and physiological roles of Kv7 channels in HPrSM.

Materials and methods: The expressions of KCNQ1-5 (Kv7 channel pore-forming α-subunits) and KCNE1-5 (β-regulatory subunits) isoforms in HPrSM were examined using real-time PCR. The relaxation effect of ML213 was investigated by cumulatively adding ML213 to the prostate strips. Kv7 currents were recorded using an amphotericin-B perforated patch-clamp technique.

Results: In HPrSM cells, KCNQ4, KCNQ5, and KCNE4 isoforms were predominantly expressed, while KCNQ1, KCNQ5, and KCNE3 isoforms were the most abundantly expressed in human prostatic tissues. Western blot analysis revealed the protein expression of the Kv7.1, 7.4, and 7.5 channel subtypes in human prostate tissues (n = 3). ML213 (an activator of Kv7.2/7.4/7.5) induced the concentration-dependent relaxation of HPrSM strips (n = 15, p = 0.001), and this effect was attenuated by pretreatment with XE991 (a Kv7.1-7.5 blocker). In electrophysiology studies, ML213 significantly increased the amplitude of whole-cell Kv7 currents in HPrSM cells. ML213-induced outward currents were greater than retigabine (a Kv7.2-7.5 channel activator). The subsequent addition of XE991 completely inhibited the ML213-induced currents (n = 9, p < 0.01 vs. ML213). ML213 hyperpolarized the HPrSM cell membrane potential and was fully reversed by XE991. In situ PLA revealed the colocalization of heteromeric KV7.4/KV7.5 channels in HPrSM cells.

Conclusions: Our findings suggest that Kv7.4 and 7.5 channels in prostatic smooth muscle play a critical role in the regulation of HPrSM tone and that Kv7 channel subtypes may be novel therapeutic targets for the treatment of LUTS associated with BPH.

Keywords: Benign prostatic hyperplasia; KCNQ potassium channels; voltage-gated potassium channels.