Triggering receptor expressed on myeloid cells (TREM)-like transcript-1 (TLT-1) is an immunoreceptor tyrosine-based inhibitory motif (ITIM)-baring TREM family protein. Triggering receptor expressed on myeloid cells (TREM) like transcript-1 (TLT-1) is a membrane protein receptor found in alpha-granules of platelets and megakaryocytes.

Trem-like transcript 1 protein, also known as Triggering receptor expressed on myeloid cells-like protein 1, TREML1 and TLT-1, is a cytoplasm and single-pass type I membrane protein. TREML1 / TLT-1 is expressed exclusively in platelets and megakaryocytes (MKs) and that its expression is up-regulated dramatically upon platelet activation. It is a receptor that may play a role in the innate and adaptive immune response. TREML1 / TLT-1 contains the characteristic single V-set immunoglobulin (Ig) domain, its longer cytoplasmic tail is composed of both a proline-rich region and an immune receptor tyrosine-based inhibitory motif, the latter known to be used for interactions with protein tyrosine phosphatases. The triggering receptors expressed on myeloid cells (TREMs) have drawn considerable attention due to their ability to activate multiple cell types within the innate immune system, including neutrophils, monocyte / macrophages, and dendritic cells, via their association with DAP12. TREML1 / TLT-1 is prepackaged, along with CD62P, into both MK and platelet alpha-granules. Differences in thrombin-induced redistribution of CD62P and TREML1 indicate that TREML1 is not simply cargo of alpha-granules but may instead regulate granule construction or dispersal. TREML1 / TLT-1 does not function to inhibit members of the TREM family but instead may play a role in maintaining vascular hemostasis and regulating coagulation and inflammation at sites of injury.