| Stem Cell Factor (SCF/KITLG), a glycoprotein growth factor, binds to the c-KIT receptor tyrosine kinase to initiate hematopoietic stem cell (HSC) maintenance, mast cell development, and primordial germ cell survival by forming SCF/c-KIT dimers that autophosphorylate receptor juxtamembrane and kinase domains, activating PI3K/AKT (for cell survival), MAPK/ERK (for proliferation), and PLCγ (for calcium mobilization) pathways that converge on gene expression changes essential for stemness and lineage commitment. SCF features a compact four-α-helical bundle with site 2 and 3 interfaces (Asp25, Leu43, Phe60) mediating high-affinity dimeric c-KIT binding, and exists as both a membrane-bound (full-length) or soluble (proteolytically cleaved) form with distinct signaling kinetics. SCF maintains HSCs in the bone marrow niche via stromal cell presentation, synergizes with TPO and FLt3L for megakaryocyte and erythroid progenitor support, drives mast cell survival, proliferation, and degranulation via KIT D816V signaling, supports melanocyte migration during development, and promotes primordial germ cell survival and migration to the gonadal ridges. The SCF/c-KIT axis forms the core hematopoietic niche signaling pathway and is a key regulator of gametogenesis; pathologically, gain-of-function KIT mutations (such as D816V and N822K) with autocrine SCF drive systemic mastocytosis, gastrointestinal stromal tumors (GIST), and acute myeloid leukemia, while therapeutic KIT inhibitors specifically target mutant-driven oncogenesis without broadly disrupting wild-type hematopoiesis. |
