PMCA1b

PMCA1b is a splice variant of the plasma membrane Ca2+-ATPase PMCA1, encoded by the ATP2B1 gene in vertebrates. The PMCA family actively extrudes cytosolic Ca2+ across the plasma membrane to the extracellular space, using energy from ATP hydrolysis. PMCA1b, like other PMCA1 variants, contributes to maintaining low resting intracellular Ca2+ and shaping Ca2+ signals in response to stimuli.

PMCA1b arises from alternative splicing of the ATP2B1 transcript and differs from other PMCA1 isoforms in its regulatory region. These differences can influence subcellular localization, interaction with regulatory proteins, and response to Ca2+-calmodulin signaling, allowing tissue- and development-stage specific Ca2+ control.

Expression patterns for PMCA1 isoforms vary by tissue and species; PMCA1b is reported in neural and certain peripheral tissues, with levels that change during development. PMCA1 activity is modulated by calmodulin, lipids, and protein interactions; in some contexts, phosphorylation and association with scaffolding proteins affect trafficking and activity.

Physiologically, PMCA1b participates in Ca2+ clearance after neuronal activity and helps maintain basal Ca2+ homeostasis. It functions together with other Ca2+ transporters such as other PMCAs and Na+/Ca2+ exchangers to regulate intracellular Ca2+ dynamics.

Genetic studies in model organisms indicate that PMCA1 is essential for development; mice lacking ATP2B1 show severe defects and lethality, underscoring the importance of PMCA1b-containing pumps in Ca2+ homeostasis.