Mitochondrial sodium/calcium antiporter that mediates sodium-dependent calcium efflux from mitochondrion, by mediating the exchange of 3 sodium ions per 1 calcium ion (PubMed:20018762, PubMed:22829870, PubMed:23056385, PubMed:24898248, PubMed:28219928). Plays a central role in mitochondrial calcium homeostasis by mediating mitochondrial calcium extrusion: calcium efflux is essential for mitochondrial function and cell survival, notably in cardiomyocytes (By similarity). Regulates rates of glucose-dependent insulin secretion in pancreatic beta-cells during the first phase of insulin secretion: acts by mediating efflux of calcium from mitochondrion, thereby affecting cytoplasmic calcium responses (PubMed:23056385). Required for store-operated Ca(2+) entry (SOCE) and Ca(2+) release-activated Ca(2+) (CRAC) channel regulation: sodium transport by SLC8B1 leads to promote calcium-shuttling that modulates mitochondrial redox status, thereby regulating SOCE activity (PubMed:28219928). Involved in B-lymphocyte chemotaxis (By similarity). Able to transport Ca(2+) in exchange of either Li(+) or Na(+), explaining how Li(+) catalyzes Ca(2+) exchange (PubMed:15060069). In contrast to other members of the family its function is independent of K(+) (PubMed:15060069). Ca(2+)(in) + 3 Na(+)(out) = Ca(2+)(out) + 3 Na(+)(in) Inhibited by the sodium/calcium exchanger inhibitor CGP-37157 (PubMed:24898248). Strongly inhibited by zinc (PubMed:15060069). Present in pancreatic beta-cells (at protein level). Phosphorylation at Ser-258 by PKA prevents calcium overload. Belongs to the Ca(2+):cation antiporter (CaCA) (TC 2.A.19) family. SLC24A subfamily. Truncated N-terminus.