# Plasma membrane calcium ATPases and cerebellar pathology: what’s the role in the ataxia?

## TL;DR

This paper explores the role of PMCA proteins in regulating calcium in neurons, particularly in cerebellar diseases like ataxia.

## Contribution

It highlights the emerging role of PMCA-Neuroplastin complexes in ultrafast calcium clearance and their potential relevance to cerebellar pathology.

## Key findings

- PMCAs facilitate ultrafast Ca²⁺ clearance at kilohertz frequencies via the PMCA-Neuroplastin complex.
- PMCAs may fine-tune Ca²⁺ microdomains through local regulation and protein interactions.
- PMCA dysfunction is linked to cerebellar pathology and ataxia, especially in Purkinje cells.

## Abstract

Ca²⁺ signaling is essential for neuronal development, migration, synaptic activity, spine plasticity, neurotransmitter release, membrane excitability, and long-term synaptic plasticity, as well as for the coupling between membrane depolarization and downstream signaling. Traditionally, Plasma Membrane Ca²⁺ ATPases (PMCAs) were considered high-affinity, low-capacity calcium extruders. However, recent evidence reveals that the PMCA-Neuroplastin complex facilitates ultrafast Ca²⁺ clearance at kilohertz frequencies, reshaping our understanding of calcium regulation, in particular in neurons. For bulk Ca²⁺ clearance, they are overshadowed by more powerful low-affinity/high-capacity systems on the plasma membrane. This raises key questions: what is the specific physiological and pathological role of PMCAs? Why do cells require a high-affinity/low-capacity, ATP-dependent extrusion mechanism? What is the functional meaning of the diversity of isoforms (four) and splice variants (over thirty)? And why do neurons localize distinct PMCA pumps to pre- and postsynaptic sites? The prevailing hypothesis is that PMCAs fine-tune Ca²⁺ microdomains through local regulation and interactions with specific protein partners. Finally, understanding their role in Purkinje cells (PCs) is particularly relevant, as alterations in PMCA function have been implicated in cerebellar pathology and ataxia.

Not applicable.