Heterodimer PMCA-basigin: Effect of the mandatory subunit on the Ca2+-ATPase activity of the plasma membrane Ca2+ ATPase

CAMILA BRUNO; ROLANDO ROSSI; CECILIA SOUTO GUEVARA; JUAN PABLO ROSSI; MARILINA DE SAUTU; IRENE C MANGIALAVORI

Congreso; Primeras Jornadas Virtuales SAB 2020; 2020

The plasma membrane Ca2+-ATPase (PMCA) is a highly regulated transporter responsible for the extrusion of Ca2+ from all eukaryotic cells. PMCA isoforms are expressed in different tissues and perform their function through the adjustment Ca2+ concentration in membrane microdomains that are related in Ca2+ signaling events. Because of this, PMCA activity is related to events ranging from cell death through apoptosis or necrosis to local regulation of actin cytoskeleton polymerization1. In humans, the variants PMCA1 and 4 are ubiquitously expressed whereas PMCA2 and 3 are expressed in specialized tissues. It has recently been discovered that neuroplastin and basigin, two glycoproteins, would act as a mandatory subunit of PMCA2. PMCA forms a heterodimer with neuroplastin or basigin depending on the neuroplastin/basigin ratio in each tissue2. The interaction of PMCA with neuroplastin/basigin is essential for its correct targeting towards the plasma membrane2. It has also been proposed that basigin or neuroplastin would be necessary for PMCA to be active3, but these studies remain controversial.The aim of this work was to study the effect of the mandatory subunit of PMCA on its Ca2+-ATPase. To this end, we used the PMCA of human erythrocytes as a model, whose majority variant is PMCA4. Since the basigin/neuplastin ratio in human erythrocytes is 30:12, we proposed that the heterodimer would be made up of PMCA and basigin. Our results showed that: (1) Basigin, but not neuroplastin, was present after purification of PMCA, (2) PMCA reconstituted in detergent micelles, was inactive in the absence of basigin; (3) PMCA reconstituted in mixed bicelles of detergent-phospholipids, was active in the absence of basigin, (4) The apparent affinity for Ca2+ and Mg2+ of PMCA in erythrocytes plasma membranes was similar to that PMCA reconstituted in mixed bicelles.