Altered Gating of Kv1.3 Channels of T Lymphocytes in Smith-Lemli-Opitz Syndrome

Abstract

The Smith-Lemli-Opitz syndrome (SLO) is a multiple congenital anomaly, caused by a decreased or abolished activity of 7-dehydrocholesterol (7DHC) reductase, which results in the accumulation of the cholesterol precursor 7DHC in the serum and potentially in the cell membrane as well. Increased 7DHC/cholesterol ratio may modify the physico-chemical properties of plasma membrane, and hence may influence the operation of the ion channels in many cell types including T cells. To test this hypothesis we compared the biophysical properties of Kv1.3 channels in T cells of SLO patients (SLO-T-cells), T-cells of healthy volunteers loaded with 7DHC (7DHC-T-cells) and control T cells. The physiological consequence of altered Kv1.3 gating was measured by the proliferative capacity of CD3+ lymphocytes.T lymphocytes were isolated from the peripheral blood of healthy volunteers (age-matched controls) and patients with SLO. 7DHC elevation in T lymphocytes membrane was achieved upon treatment with cyclodextrin/7DHC complex. Kv1.3 currents were measured using whole-cell patch-clamp. Proliferation rate of lymphocytes was assessed with CFSE-dilution assay upon anti-CD3/anti-CD28 stimulation.Our results showed that both activation and inactivation kinetics were significantly slower, and the midpoint of the steady-state activation was shifted toward positive voltages in the SLO-T-cells compared to control (taua,SLO: 0.72 ms, taua,c: 0.60 ms ; taui,SLO: 238,48 ms, taui,c : 213,19 ms; V1/2,SLO : - 21.762 mV ,V1/2,c : - 27.98 mV). Qualitatively and quantitatively differences in the gating of Kv1.3 channels were observed in 7DHC-T-cells vs. control. T-cells from SLO patients had decreased proliferation rate as compared to healthy controls. These data demonstrate that elevated 7DHC level of cell membrane can modify the operation of ion channels and may contribute to the neurodegenerative defects in SLO. (Mecenatura OSTRAT/260/2012, TAMOP 4.2.4.A/2-11-1-2012-0001).