Calsequestrin 1 Protein, Human

Calsequestrin 1, a high-capacity calcium-binding protein, serves as an internal calcium store in muscle. Clusters of acidic residues at the protein surface, particularly at the subunit interface, facilitate the binding of approximately 80 Ca(2+) ions. This protein plays a pivotal role in regulating the release of lumenal Ca(2+) through the calcium release channel RYR1, thereby contributing to the initiation of muscle contraction. Additionally, Calsequestrin 1 acts as a negative regulator of store-operated Ca(2+) entry (SOCE) activity. Existing as a monomer that increases in response to intracellular calcium depletion, it can also form homodimers and higher-order homooligomers, with Ca(2+) ions promoting oligomerization. Calsequestrin 1 interacts with STIM1, preferentially in its monomeric form, and this interaction intensifies following intracellular calcium depletion. Furthermore, it interacts with ASPH and TRDN, highlighting its involvement in diverse cellular processes related to calcium homeostasis.