Evidence of direct binding of G-actin to PMCA by Surface Plasmon Resonance

DALGHI M; FERNÁNDEZ M; MALCHIODI E; ROSSI JP

Salta

Congreso; Joint Meeting of the 3º Latin American Protein Society Meeting and the XXXVIII Annual Meeting of the Argentinean Biophysical Society; 2010

Sociedad Argentina de Biofísica

Plasma Membrane Calcium ATPase (PMCA) expels Ca2+ from all eukaryotic cell types - where is present in an amount that does not exceed 0.1% of the total membrane proteins- mantaining the intracellular Ca2+ levels at a submicromolar range.PMCA’s traditional activator is calmodulin which is assumed to free it from autoinhibition. The activity of the pump is also influenced by the phospholipid composition in the plasma membrane, by phosphorylation and cleavage of the molecule and by self-association.Previous studies of our laboratory (Vanagas et al., 2007) suggest that the main isoform of the pump expressed in erythrocytes, hPMCA4b, interacts with the actin cytoskeleton which can regulate both the catalytic and transport activity of the enzyme. Recent observations demonstrate that while G-actin and short oligomers seem to activate the pump, F-actin may inhibit it.To further explore this novel regulatory mechanism, we decided to investigate the interaction between PMCA and G-actin which not only constitutes one of the states of actin responsible for the enhancement of PMCA activity but also represents half of the total actin content in most cell types.