Correspondences between the binding characteristics of a non-natural peptide, Lei-Dab7, and the distribution of SK subunits in the rat central nervous system.

Small-conductance calcium-activated potassium channels (SK1-SK3 channels) are responsible for long-lasting hyperpolarization following action potential and contribute to the neuronal firing and integration signal. Two peptide toxins: apamin and Leiurotoxin 1, block this SK channels with high affinities. We generated a modified Leiurotoxin 1 (Lei-Dab7) that inhibits SK2 channels with a high selectivity. Competitive binding of radio-iodinated apamin to different rat brain structures, in the presence of native apamin and Lei-Dab7, has shown that dissociation constants differ by a factor of 1000 and thus demonstrated that ligand affinity is as important as ligand selectivity for a specific receptor. However, the lack of ligands discriminating between SK channel subunits is impeding the understanding of the role of each heteromeric SK channel type in different tissues. Our study aims to better understand the molecular combinations of SK channels and their association with specific functional implications. On this purpose, a clustering technique allows us to identify five groups of brain structures reflecting singular profiles of affinity and selectivity of Lei-Dab7 in comparison with apamin. The analysis of correspondences between Lei-Dab7 binding and distribution of SK subunits in these groups of brain structures suggests that functional heteromeric SK channels are involved in specific information processes.