Annexin A2-S100A10 Represents the Regulatory Component of Maxi-Cl Channel Dependent on Protein Tyrosine...

Maxi-anion channel (Maxi-Cl) is ubiquitously expressed and involved in a number of important cell functions especially by serving as an ATP release pathway. We recently identified SLCO2A1 as its essential core component. However, the regulatory component required for the channel activation/inactivation remains unidentified.

In the present study, to identify the regulatory component, we made genome-wide analysis combined with siRNA screening and performed patch-clamp studies and ATP release assay after gene silencing and overexpression.

Comparative microarray analysis between Maxi-Cl-rich C127 and -deficient C1300 cells revealed highly differential expression not only of SLCO2A1 but also of four annexin family members. Gene silencing study showed that Anxa2 is involved in Maxi-Cl activity. The Maxi-Cl events appeared in C1300 cells by overexpression of Slco2a1 and more efficiently by that of Slco2a1 plus Anxa2. Immunoprecipitation assay supported the interaction between ANXA2 and SLCO2A1. Suppressive effects of overexpression of a phospho-mimicking mutant of Anxa2, Anxa2-Y23E, indicated that protein tyrosine dephosphorylation dependence of Maxi-Cl is conferred by ANXA2. Maxi-Cl activity was suppressed by gene silencing of S100A10, a binding partner of ANXA2, and by applying a synthetic ANXA2 peptide, Ac-(1-14), which interferes with the ANXA2-S100A10 complex formation. Intracellular Ca²⁺ dependence of Maxi-Cl activity was abolished by S100a10 knockdown.

The ANXA2-S100A10 complex represents the regulatory component of Maxi-Cl conferring protein tyrosine dephosphorylation dependence and intracellular Ca²⁺ sensitivity on this channel.