REGULATION OF P-ATPASES BY THE CYTOSKELETON

JUAN PABLO F.C. ROSSI

Buzios, Rio de Janeiro, Brasil

Conferencia; VII Iberoamerican Congress of Biophysics 2009; 2009

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman";} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt; mso-ascii-font-family:Calibri; mso-fareast-font-family:Calibri; mso-hansi-font-family:Calibri;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> REGULATION OF P-ATPASES BY THE CYTOSKELETON The cytoskeleton is a network of protein filaments which occupy the interior of all plant and animal cells. It acts as a support for the organization and fixation of organelles and enzymes. It is formed by three main types of protein filaments: microtubules, actin and intermediate filaments, bound together and to other cellular structures. The controlled polymerization of actin and tubulin is responsible for both the mobility and shape of eukaryotic cells. The movement of eukaryotic cells is the result of the coordinated action of the formation of extensions, adhesions and retractions of the membrane, where the actin network and the interactions between these and molecular motors play a key role. When the specific activity of the plasma membrane calcium ATPase (PMCA) in isolated red blood cell membranes is measured as a function of the protein concentration, the specific activity is not constant but shows an activation-inhibition behavior. Modifying the actin cytoskeleton with cytochalasin D showed that this activation-inhibition behavior is likely due to the interaction between PMCA and the cytoskeleton. This raised the hypothesis that the activation-inhibition of the specific activity of PMCA depends on the state of polymerization of the cytoskeletal proteins that can thereby modify the activity of calcium transport. Our results show that monomeric or G-actin is responsible for the activation of PMCA and filamentous or F-actin produces the inhibition of PMCA. We have identified in different PMCA isoforms likewise that in other P-ATPases as the sodium pump and the sarcoendoplasmic Ca2+-ATPase that the cytoskeleton, namely actin filaments, interact with P-ATPases modulating its activity. This phenomenon seems to be a general property of all membrane proteins in which the cytoskeleton is no longer restricted to a merely mechanical function, but rather would produce the regulation of the activity of the integral proteins to which it is related.