Function
ABL1, a non-receptor tyrosine-protein kinase, plays a crucial role in various cellular processes associated with growth and survival, including cytoskeleton remodeling in response to extracellular stimuli, cell motility and adhesion, receptor endocytosis, autophagy, DNA damage response, and apoptosis. ABL1 coordinates actin remodeling through tyrosine phosphorylation of proteins that regulate cytoskeleton dynamics, such as WASF3 (involved in branch formation); ANXA1 (involved in membrane anchoring); DBN1, DBNL, CTTN, RAPH1, and ENAH (involved in signaling); or MAPT and PXN (microtubule-binding proteins). Phosphorylation of WASF3 is essential for the stimulation of lamellipodia formation and cell migration. ABL1 is involved in regulating cell adhesion and motility through phosphorylation of key regulators of these processes, such as BCAR1, CRK, CRKL, DOK1, EFS, or NEDD9. It also phosphorylates multiple receptor tyrosine kinases, particularly promoting endocytosis of EGFR, facilitating the formation of neuromuscular synapses through MUSK, inhibiting PDGFRB-mediated chemotaxis, and modulating the endocytosis of activated B-cell receptor complexes. Other substrates involved in endocytosis regulation include caveolin (CAV1) and RIN1. Additionally, ABL1 regulates the CBL family of ubiquitin ligases, which drive receptor down-regulation and actin remodeling. Phosphorylation of CBL leads to increased EGFR stability. ABL1 is involved in late-stage autophagy by positively regulating the trafficking and function of lysosomal components. In response to oxidative stress, ABL1 translocates to mitochondria, mediating mitochondrial dysfunction and cell death. It phosphorylates serine/threonine kinase PRKD2 at 'Tyr-717' in response to oxidative stress. ABL1 is also translocated to the nucleus, where it exhibits DNA-binding activity and participates in DNA-damage response and apoptosis. Many known substrates mediate DNA repair, including DDB1, DDB2, ERCC3, ERCC6, RAD9A, RAD51, RAD52, or WRN. When DNA damage is too severe to repair, ABL1 activates the proapoptotic pathway. It phosphorylates TP73, a primary regulator of damage-induced apoptosis, and the caspase CASP9 on 'Tyr-153', regulating its processing in the apoptotic response to DNA damage. ABL1 also phosphorylates PSMA7, leading to inhibition of proteasomal activity and cell cycle transition blocks. ABL1 acts as a regulator of multiple pathological signaling cascades during infection. Several known tyrosine-phosphorylated microbial proteins have been identified as ABL1 substrates, including A36R of Vaccinia virus, Tir (translocated intimin receptor) of pathogenic E. coli and possibly Citrobacter, CagA (cytotoxin-associated gene A) of H. pylori, or AnkA (ankyrin repeat-containing protein A) of A. phagocytophilum. Pathogens can hijack ABL1 kinase signaling to reorganize the host actin cytoskeleton for various purposes, such as facilitating intracellular movement and host cell exit. Finally, ABL1 functions as its own regulator through autocatalytic activity and through phosphorylation of its inhibitor, ABI1. It regulates T-cell differentiation in a TBX21-dependent manner by phosphorylating TBX21 on tyrosine residues, enhancing its transcriptional activator activity.