CD135

Cluster of differentiation antigen 135 (CD135) also known as Fms-like tyrosine kinase 3 (FLT-3), receptor-type tyrosine-protein kinase FLT3, or fetal liver kinase-2 (Flk2) is a protein that in humans is encoded by the FLT3 gene. FLT3 is a cytokine receptor which belongs to the receptor tyrosine kinase class III. CD135 is the receptor for the cytokine Flt3 ligand (FLT3L).

It is expressed on the surface of many hematopoietic progenitor cells. Signalling of FLT3 is important for the normal development of haematopoietic stem cells and progenitor cells.

The FLT3 gene is one of the most frequently mutated genes in acute myeloid leukemia (AML). Besides, high levels of wild-type FLT3 have been reported for blast cells of some AML patients without FLT3 mutations. These high levels may be associated with worse prognosis.

Structure

FLT3 is composed of five extracellular immunoglobulin-like domains, a transmembrane domain, a juxtamembrane domain and a tyrosine-kinase domain consisting of 2 lobes that are connected by a tyrosine-kinase insert. Cytoplasmic FLT3 undergoes glycosylation, which promotes localization of the receptor to the membrane.