The function of TSPAN4 (tetraspanin 4, ENSG00000214063) is as follows. Structural component of specialized membrane microdomains known as tetraspanin-enriched microdomains (TERMs), which act as platforms for receptor clustering and signaling. Plays an essential role in migrasome formation and migration on retracting fibers at the rear end of migrating cells (PubMed:31371828). Migrasomes are cellular organelles that form as large vesicle-like structures on retraction fibers of migrating cells (PubMed:31371828). Mechanistically, acts as a membrane curvature sensor and participates in stabilizing the migrasome structure in a late stage of biogenesis (PubMed:36252000, PubMed:36823145). May also play a regulatory role for the histamine H4 receptor/HRH4 without affecting histamine binding to HRH4 or signaling (PubMed:34439793). {ECO:0000269|PubMed:31371828, ECO:0000269|PubMed:34439793, ECO:0000269|PubMed:36252000, ECO:0000269|PubMed:36823145}.