¨Plasma Membrane Calcium Pump regulation by the Cytoskeleton¨

VANAGAS, L.; MANGIALAVORI IRENE; ROLANDO ROSSI; ROSSI, J.P.F.C.

MONTEVIDEO, URUGUAY

Congreso; 34th Annual Meeting of the Argentine Biophysical Society; 2007

SOCIEDAD ARGENTINA DE BIOFISICA

  ¨Plasma Membrane Calcium Pump regulation by the Cytoskeleton¨. SAB Vol 34. p 118. Vanagas.L., Mangialavori, IC., Rossi, RC. And Rossi, JPFC   When we measure the specific activity of the PMCA in isolated red blood cell membranes as a function of the protein concentration, the specific activity is not constant but it presents an activation-inhibition behavior. We call this effect the ¨dilution phenomenon¨. When we modified the cytoskeleton of actin with cytochalasin D, we found that the activation-inhibition behavior could be assigned to the interaction between PMCA and actin. These preliminary results allowed us to raise the hypothesis that the phenomenon of activation-inhibition of the specific activity of PMCA could be assigned to its interaction with the cytoskeleton proteins, which according to their state would modify the activity of calcium transport. Results in this paper show that: (1) monomeric or G actin produces the activation of PMCA; (2) filamentous or F actin produces the inhibition of PMCA. Such results were also observed measuring the phosphorylation of the enzyme and the transport of calcium. (3) The effects of actin on PMCA are the expression of the direct interaction of the enzyme with actin. (4) The dilution phenomenon seems to be a general property of membrane proteins in which the underlying cytoskeleton could be a regulator of the enzymatic activity.