The granulocyte colony-stimulating factor receptor (G-CSF-R) is a transmembrane protein composed of an immunoglobulin-like (Ig-like) domain, a cytokine receptor homology (CRH) domain, and three fibronectin type III (FN III) domains. G-CSF-R is expressed across all granulocyte lineages, including progenitor cells, and has also been detected in monocytes, T and B lymphocytes, and non-hematopoietic tissues such as cardiomyocytes and neural stem cells. Its primary ligand is the cytokine granulocyte colony-stimulating factor (G-CSF). Lacking intrinsic tyrosine kinase activity, G-CSF-R undergoes a conformational change upon ligand binding, leading to the activation of downstream signaling pathways including Jak/Stat, PI3K/Akt, and MAPK. G-CSF promotes the differentiation and proliferation of myeloid progenitors into neutrophils. Mutations in the G-CSF-R gene, CSF3R, are associated with multiple disorders, including severe congenital neutropenia (SCN), chronic neutrophilic leukemia (CNL), and atypical chronic myeloid leukemia (aCML).
