F-actin-binding domain of c-Abl regulates localized phosphorylation of C3G: role of C3G in c-Abl-mediated cell death.
The c-Abl tyrosine kinase maintains cellular homeostasis through its ability to regulate apoptosis and actin dynamics. In vivo, c-Abl activity is stringently regulated and mechanisms involved are not fully understood. Here, we identified the Rap1 guanine nucleotide exchange factor, C3G (RapGEF1), as a substrate and an effector of c-Abl-mediated functions. Ectopic expression of c-Abl in mammalian cell lines, known to induce apoptosis, resulted in phosphorylation of endogenous C3G on Y504 coincident with cell detachment and chromatin condensation. Phosphorylation of C3G coincided with restricted c-Abl activation in regions rich in actin, and was dependent on cellular F-actin dynamics. Unlike C3G or c-Abl, p-C3G was resistant to detergent extraction, suggesting its enhanced affinity for the cytoskeleton. Localized C3G phosphorylation and coincidence with cells undergoing cell death was dependent on F-actin-binding domain (FABD) of c-Abl. Activation of endogenous c-Abl by oxidative stress was associated with phosphorylation of cellular C3G on Y504. Inhibition of C3G expression and function using RNAi or dominant-negative approaches inhibited c-Abl-mediated cell death. These findings identify C3G as a novel target of c-Abl and also show that FABD of c-Abl is essential for regulation of its restricted activation to induce apoptosis.
Mitra
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Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research (CSIR), Uppal Road, Hyderabad, India.
Radha
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V
D000199:Actins / Q000378:metabolism*; D000906:Antibodies / Q000276:immunology / Q000378:metabolism; D017209:Apoptosis; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D020735:Guanine Nucleotide-Releasing Factor 2 / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D016315:Proto-Oncogene Proteins c-abl / Q000737:chemistry* / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D000199:Actins; D000906:Antibodies; D020735:Guanine Nucleotide-Releasing Factor 2; D014443:Tyrosine; D016315:Proto-Oncogene Proteins c-abl