How many Ca²+ATPase isoforms are expressed in a cell type? A growing family of membrane proteins illustrated by studies in platelets

Abstract

Ca²⁺ signaling plays a key role in normal and abnormal platelet functions. Understanding platelet Ca²⁺ signaling requires the knowledge of proteins involved in this process. Among these proteins are Ca²⁺ATPases or Ca²⁺ pumps that deplete the cytosol of Ca²⁺ ions. Here, we will particularly focus on two Ca²⁺ pump families: the plasma membrane Ca²⁺ATPases (PMCAs) that extrude cytosolic Ca²⁺ towards the extracellular medium and the sarco/endoplasmic reticulum Ca²⁺ATPases (SERCAs) that pump Ca²⁺ into the endoplasmic reticulum (ER). In the present review, we will summarize data on platelet Ca²⁺ATPases including their identification and biogenesis. First of all, we will present the Ca²⁺ATPase genes and their isoforms expressed in platelets. We will especially focus on a member of the SERCA family, SERCA3, recently found to give rise to a number of species-specific isoforms. Next, we will describe the differences in Ca²⁺ATPase patterns observed in human and rat platelets. Last, we will analyze how the expression of Ca²⁺ATPase isoforms changes during megakaryocytic maturation and show that megakaryocytopoiesis is associated with a profound reorganization of the expression and/or activity of Ca²⁺ATPases. Taken together, these data provide new aspects of investigations to better understand normal and abnormal platelet Ca²⁺ signaling.

• Platelets
• megakaryocytes
• Ca2+
• Ca2+ATPases
• isoforms