Regulation of Ca2+ ATPases by their N- and C-termini

A total of nine P-type Ca2+ ATPases exist in humans, each represented by multiple splice variants. Although the domain organization and pumping mechanism is well-conserved within the human Ca2+ transporter isoforms, their N- and C-terminal stretches are highly variable and contain isoform-specific regulatory elements. Here, we describe two intracellular Ca2+ pumps, SPCA and SERCA2, which are respectively located in the Golgi/secretory pathway and sarco/endoplasmic reticulum (ER). First, we focus on the activation mechanism of the plasma membrane Ca2+ channel Orai1 by the N- and C-terminal stretches of SPCA1a/2, which are both upregulated in mammary gland during lactation and certain types of breast cancer. SPCA2 is already known to constitutively activate Orai1. We further explore this interaction, and investigate whether SPCA1a, like SPCA2, activates Orai1. In the second part, we study the Ca2+ affinity regulation of the SERCA2 splice variants, in particular the affinity-increasing effect of the long C-terminal tail of SERCA2b (2b-tail). The shorter splice variant SERCA2a is implicated in heart failure, and SERCA2b provides an interesting template for rational drug design of compounds that enhance Ca2+ affinity of SERCA2a. The aim is to gain insight in the mechanism of the 2b-tail, with the goal of developing a pharmacophore model, which is screened against an in silico compound library for LE mimetics. Hit compounds will be tested for their effect on SERCA2a activity.status: publishe