Calpain small subunit 1, also known as CAPN4, is a protein that in humans is encoded by the CAPNS1gene.
Calpains are a ubiquitous, well-conserved family of calcium-dependent, cysteine proteases. Calpain families have been implicated in neurodegenerative processes, as their activation can be triggered by calcium influx and oxidative stress. Calpain I and II are heterodimeric with distinct large subunits associated with common small subunits, all of which are encoded by different genes. Two transcript variants encoding the same protein have been identified for this gene.
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