Perisynaptic organization of plasma membrane calcium pumps in cerebellar cortex

Abstract

Calcium, a ubiquitous intracellular messenger, regulates numerous intracellular signaling pathways. To permit specificity of signal transduction and prevent unwanted cross-talk between pathways, sites of calcium entry in neurons are localized to specific membrane domains. To test whether Ca(2+) extrusion pumps might exhibit analogous compartmentalization, we used immunohistochemistry to determine the subcellular localization of the two main plasma membrane Ca(2+)-ATPase (PMCA) isoforms in the cortex of the rat cerebellum. We find that both PMCA2 and PMCA3 are targeted to distinct compartments within the plasma membrane. In the molecular layer, both isoforms were at highest levels within synaptic profiles, but PMCA2 was postsynaptic and PMCA3 was presynaptic. Moreover, inside these compartments, both pumps exhibited nonuniform distributions. These data imply that cerebellar neurons possess remarkably effective mechanisms to target and restrict PMCA2 and -3 to specific membrane domains, raising the possibility that calcium pumps contribute to local Ca(2+) signaling.

Ultrastructure of Synapses in the Mammalian Brain

“…Both SDS-FRL and standard pre-embedding techniques have identified a variety of voltage-dependent potassium channels in spine membranes, including K V 1, K V 3, K V 4, K ir 3, HCN, BK, and TASK subtypes (Lorincz et al 2002;Luján et al 2003;Callahan et al 2004;Notomi and Shigemoto 2004;Burkhalter et al 2006;Kulik et al 2006;Kaufmann et al 2009;Puente et al 2010). In addition, several transporters and pumps have been detected within the spine plasma membrane, including glutamate transporters (He et al 2000), the calcium exchanger NCX1 (Lorincz et al 2007), and multiple PMCA isoforms (Burette and Weinberg 2007;Burette et al 2009Burette et al , 2010Kenyon et al 2010). It seems likely that other pumps (e.g., the Na þ -K þ ATPase) are also present, but immunogold data are not yet available.…”

Plasma Membrane Ca2+-ATPase Isoforms Composition Regulates Cellular pH Homeostasis in Differentiating PC12 Cells in a Manner Dependent on Cytosolic Ca2+ Elevations

“…Due to the abundance of PMCA2 and PMCA3 in the nervous system they are termed neuron-specific. During development their expression undergoes considerable changes reflecting the importance of the spatial organization of Ca 2+ extrusion systems for synaptic formation [17]–[19]. Moreover, the observation of mRNA distribution suggests that the expression of PMCA2 and PMCA3 is controlled by different mechanisms than the two other isoforms [20].…”

Mutation of plasma membrane Ca 2+ ATPase isoform 3 in a family with X-linked congenital cerebellar ataxia impairs Ca 2+ homeostasis

“…In the molecular cell layer of the cerebellum, PMCA2 and PMCA3 concentrate in synaptic regions [parallel excitatory fiber (PF)-Purkinje neuron (PN) synapse] with a complementary distribution: high levels of PMCA3 are associated with the axon terminals of granule cells (PF terminals/presynaptic side), whereas PMCA2 is most abundant in PN dendrites (PN-postsynaptic side). During development, the up-regulation of PMCA2 and -3 in dendrites and dendritic spines coincides with their maturation, reflecting the importance of the proper spatial organization of Ca 2+ -extrusion systems for synaptic formation (4,5). Studies on PMCA3 are much scarcer than those on the other three basic isoforms.…”