STRUCTURAL CORRELATES UNDERLYING GAP JUNCTION HEMICHANNEL COUPLING
01/30/2020
Ágnes Simon1, László Héja1, Csaba Magyar2, Julianna Kardos1
1 Institute for Organic Chemistry and 2Institure for Enzimology, Research Centre for Natural Sciences, Budapest, Hungary
Intercellular gap junction channel (GJC) contacts play significant role in the development, signalling as well as malfunctions of brain tissue. Detailed understanding of GJ hemichannel (HC) coupling and pharmacological manipulation of GJ and HC functions, however, are long-time limited by the lack of specific GJC inhibitors. Among ideas about the nature of forces keeping GJCs together, protein stabilization centres (SCs) has not been studied as yet. Here we used SC analysis of and molecular docking into astrocyte-specific Cx43 and neuron-specific Cx36 connexin HCs to explore potential targetable sequences of these proteins.We hypothesized that reconfiguration of SCs at the extracellular loop domains (EL1 and EL2) of GJ HCs may provide specific inhibitory sites. GJC HCs built of Cx36 and Cx43 proteins have been modelled and compared. In order to explore potentially distinguishable structures of extracellular loop domains, molecular dynamics calculations have been performed on Cx36 and Cx43 GJ HCs. Extracellular SCs forming EL1 repeat sequence with cysteine, C55-N56-T57 in Cx36 HC and C54-N55-T56 in Cx43 HC, suggest that the possible disulfide bond exchange appearing in HC coupling into GJC shall rearrange vicinal L58 and Q57 containing SCs, as well. In addition, docking calculations predict the interaction of EL2 sequence analogue peptide inhibitors with SCs T57-L58 in Cx36 HC or T56-Q57 in Cx43 HC. The findings may substantiate the mechanism of inhibition of HC coupling to GJC as being specifically associated with peptide inhibitor binding to the EL1 loop SCs. In view of protein sequences of known Cx GJCs in humans, it seems likely for several isoforms to be engaged similarly. This work was supported by grants VEKOP-2.1.1-15-2016-00156 and National Research, Development and Innovation Office grant OTKA K124558