Pathophysiological modulation of Kv1.5 in the cardiovascular systemRole of SIGMA-1 receptor

Resumen

Kv1.5 channels generate the atria-selective current IKur in the heart and control pulmonary vascular tone. Their dysfunction is a common feature in diseases such as atrial fibrillation (AF) and pulmonary arterial hypertension (PAH), thus being considered as potential targets for the development of new drugs. It is remarkable that different mutations in genes encoding K+ channels have been described in heritable PAH. Likewise, reduced expression and/or activity of Kv1.5 channels has been reported in human or experimental PAH and single nucleotide polymorphisms in its KCNA5 gene have been found in PAH patients, which suggest that Kv1.5 channel dysfunction may be a risk factor for PAH. The sigma-1 receptor (S1R) is an endoplasmic reticulum chaperone ubiquitously expressed with diverse functions. Upon stimulation, it translocates to the plasma membrane, hence interacting, among others, with ion channels. In this Doctoral Thesis, we have first analysed the interaction between Kv1.5 and S1R; as a new approach to modulate Kv1.5 function. Second, we have functionally characterised seven different KCNA5 variants found in a Spanish cohort of PAH patients. By using different electrophysiological and molecular techniques, we have demonstrated that S1R physically interacts with Kv1.5, as the former modulates the expression of the latter in the plasma membrane. Correspondingly, TEVC experiments in X. laevis oocytes showed that high S1R concentrations decreased the current amplitude of Kv1.5 but low concentrations increased it. However, the time and voltage-dependent characteristics of the Kv1.5 current were not modified by the presence of S1R in transfected HEK293 cells. S1R agonists (PRE084 and SKF10047) increased Kv1.5 expression, whereas the S1R antagonist BD1047 decreased it. Likewise, human samples of AF and PAH showed lower KV1.5 and S1R expression compared to control ones. Moreover, PRE084 increased Kv1.5 currents and decreased contraction in rat pulmonary arteries. Finally, we observed a decrease in the proliferation of human pulmonary artery smooth muscle cells. We also found that, KCNA5 variants found in PAH patients (namely, p.Arg184Pro and p.Gly384Arg) resulted in a clear loss of potassium channel function. This Kv1.5 channel dysfunction was associated with impaired apoptosis and enhanced viability of human pulmonary artery smooth muscle cells. This Thesis provides insight into the potential role of S1R modulating Kv1.5 channels and its possible beneficial role in the cardiovascular system and encourages the idea that KCNA5 pathogenic variants may be a developing factor for PAH.