A new human gene KCNRG encoding potassium channel regulating protein is a cancer suppressor gene candidate located in 13q14.3

Abstract

We report the primary characterization of a new gene KCNRG mapped at chromosome band 13q14.3. This gene includes three exons and has two alternatively spliced isoforms that are expressed in normal tissues and in some tumor cell lines. Protein KCNRG has high homology to tetramerization domain of voltage-gated K + channels. Using the patchclamp technique we determined that KCNRG suppresses K + channel activity in human prostate cell line LNCaP. It is known that selective blockers of K + channels suppress lymphocyte and LNCaP cell line proliferation. We suggest that KCNRG is a candidate for a B-cell chronic lymphocytic leukemia and prostate cancer tumor suppressor gene. ß

Genetic and expression analysis of the KCNRG gene in hepatocellular carcinomas

“…The voltage-dependent K + channel activity was measured to determine the effect of a mutation of KCNRG, as described previously (Ivanov et al, 2003). The LNCaP cells showed a large noninactivating voltage-dependent K + current with an incremental membrane voltage step ( Figure 4A).…”

“…Surprisingly, all the cell lines expressed the KCNRG transcript (data not shown). Therefore, LNCap cells, which showed dramatic inhibition of K + fluxes of KCNRG, were used (Ivanov et al, 2003). The LNCaP cells transfected with either the wild-or mutant-type of the KCNRG gene were grown on a coverslip at a density of 2.0 × 10 5 /ml in the medium for 2 days after transfection.…”

“…The LNCaP cells transfected with either the wild-or mutant-type of the KCNRG gene were grown on a coverslip at a density of 2.0 × 10 5 /ml in the medium for 2 days after transfection. The whole-cell patch clamp method was used to measure the activity of the voltage-dependent K + channels, as previously described (Ivanov et al, 2003). The cells on a coverslip were transferred to the recording chamber and superfused continuously with the extracellular solution (1.5-2 ml/min) containing 125 mM NaCl, 2.5 mM KCl, 2 mM CaCl2, 1 mM MgSO4, 1.25 mM KH2PO4, 25 mM NaHCO3, and 10 mM D-glucose, bubbled with 95% O2 and 5% CO2 (290-295 mOsm).…”

“…The measured osmolarity of the pipette solution was 286 mOsm. In order to prevent possible contamination of the calcium-dependent K + channels (Skryma et al, 1999;Kim et al, 2001;Ivanov et al, 2003), the free calcium concentration of the pipette solution was buffered with 10 mM BAPTA to 0.04 M, calculated using 'WinMAXC' software (from Chris Patton, Hopkins Marine Station, Stanford University, CA). The cells showing a bright green fluorescence on the fluorescence microscope were chosen.…”

“…Interestingly, drugs blocking these K + channels, such as quinine and glibenclamide, inhibit the growth of many types of cells, ranging from quiescent lymphocytes stimulated by mitogens to rapidly cycling tumor cells, and arrest the cell cycle Wonderlin et al, 1996). Recently, Ivanov et al identified a new tumor suppressor gene, the KCNRG gene, which encodes a potassium channel regulating protein and located in 13q14.3 (Ivanov et al, 2003). Therefore, the inactivation of the KCNRG through primary structural changes, such as mutations and allelic losses, might be involved in the development or progression of various human cancers, including HCC.…”