Fgr

Fgr is a Src family tyrosine kinase activated during β2 integrin-dependent signaling in human neutrophils, linking adhesion to protein tyrosine phosphorylation^[1]. Mechanistically, Fgr and Hck support adhesion-dependent neutrophil respiratory burst, spreading, and degranulation, showing that Fgr participates in integrin-driven inflammatory effector functions^[2][3]. Fgr also acts with Hck to negatively regulate neutrophil and dendritic-cell chemokine signaling through PIR-B, indicating a context-dependent role in myeloid signal control^[4]. In disease models, hematopoietic loss of Hck, Fgr, and Lyn protected mice from autoantibody-induced arthritis, blistering skin inflammation, and reverse passive Arthus reaction by impairing inflammatory-environment generation rather than intrinsic leukocyte recruitment^[5]. Compared with related Src family isoforms, Fgr shows substantial functional overlap with Hck and Lyn, because single Fgr deficiency did not block arthritis development, whereas combined Hck/Fgr/Lyn loss produced complete protection^[5]. For experimental applications, an Fgr kinase inhibitor attenuated sepsis-associated encephalopathy by reducing mitochondrial dysfunction, oxidative stress, and neuroinflammation through the SIRT1/PGC-1α pathway^[6].