Title

 

Authors

A.A. Nasti¹ , F. Alessandrini², V. Lariccia¹ , M. Pesaresi¹, A. Tagliabracci² , S. Amoroso^1
 
1Section of Pharmacology, Department of Neuroscience, University “Politecnica delle Marche”, Ancona, Itay; ² Section of Legal Medicine, Department of Neuroscience, University “Politecnica delle Marche”, Ancona, Italy

 

Abstract

Long-QT syndrome (LQTS) is a potentially lethal, inheritable arrhyithmia syndrome, stemming from perturbed cardiac repolarization and affecting about 1 in 3000 persons. The pathogenetic basis for LQTS has focused on ion channels: more than 200 mutations in 7 cardiac sarcolemmal, Na+, K+ and Ca2+ ion channel subunit genes account for about 75% of LTQS.  Recently, 2 LQTS-susceptibility genes encoding for two non-ion channel proteins have been discovered. The first gene encodes an adapter protein, ankyrin B, which partecipates in localization of sodium and calcium channels to the sarcolemma; the second one encodes caveolin-3, the major scaffolding protein present in caveolae in the heart: mutations in both genes result in secondarily ion channels disruption as consequence of altered localization or function (Zhou et al, 2006; Vatta et al; 2006). In this study we sought to investigate whether a de novo CAV3 mutation, found in 1 out of 50 unrelated Italian patients with LTQS, may be implicated in this syndrome. Patient was negative to mutational analyses of the entire coding region of other LQTS-associated genes. We performed a mutation analysis of the caveolin-3 nucleotide variant verifying that it was a missense mutation (V82I), localized to the intra-membrane domain of caveolin-3, and it modified highly conserved amino acids of the protein across species. The human wild-type CAV3 and the V82I-CAV3 mutant were cloned in a plasmid and transfected in BHK cell line. We found that the expression and the distribution of V82I-CAV3 and WT-CAV3 proteins are quite similar in this system. However cells expressing the mutant CAV3 are significantly more susceptible to the death under stressing conditions. In addition, preliminary data indicate that the mutant V82I-CAV3 affects the sodium-calcium exchanger (NCX1). In particular, when we transfected V82I-CAV3 in BHK cell line stable expressing NCX1, the activity of the exchanger resulted compromised.These results could be clinically relevant considering that NCX1 localized to caveolae, due to its association with caveolin 3 (Bossuyt et al, 2002), and that abnormal distribution or activity of NCX1 can lead to an arrhythmic response (Collins et al, 2005; Kukielka et al, 2011).
Collectively, these data suggest that the V82I mutation found in CAV3 can be potentially involved in congenital Long-QT syndrome, affecting survival signaling pathways and/or the NCX1 functionality.