A novel role of Sprouty 2 in regulating cellular apoptosis.
Sprouty (SPRY) proteins modulate receptor-tyrosine kinase signaling and, thereby, regulate cell migration and proliferation. Here, we have examined the role of endogenous human SPRY2 (hSPRY2) in the regulation of cellular apoptosis. Small inhibitory RNA-mediated silencing of hSPRY2 abolished the anti-apoptotic action of serum in adrenal cortex adenocarcinoma (SW13) cells. Silencing of hSPRY2 decreased serum- or epidermal growth factor (EGF)-elicited activation of AKT and ERK1/2 and reduced the levels of EGF receptor. Silencing of hSPRY2 also inhibited serum-induced activation of p90RSK and decreased phosphorylation of pro-apoptotic protein BAD (BCL2-antagonist of cell death) by p90RSK. Inhibiting both the ERK1/2 and AKT pathways abolished the ability of serum to protect against apoptosis, mimicking the effects of silencing hSPRY2. Serum transactivated the EGF receptor (EGFR), and inhibition of the EGFR by a neutralizing antibody attenuated the anti-apoptotic actions of serum. Consistent with the role of EGFR and perhaps other growth factor receptors in the anti-apoptotic actions of serum, the tyrosine kinase binding domain of c-Cbl (Cbl-TKB) protected against down-regulation of the growth factor receptors such as EGFR and preserved the anti-apoptotic actions of serum when hSpry2 was silenced. Additionally, silencing of Spry2 in c-Cbl null cells did not alter the ability of serum to promote cell survival. Moreover, reintroduction of wild type hSPRY2, but not its mutants that do not bind c-Cbl or CIN85 into SW13 cells after endogenous hSPRY2 had been silenced, restored the anti-apoptotic actions of serum. Overall, we conclude that endogenous hSPRY2-mediated regulation of apoptosis requires c-Cbl and is manifested by the ability of hSPRY2 to sequester c-Cbl and thereby augment signaling via growth factor receptors.
Edwin
Francis
F
Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois 60153.
Patel
Tarun B
TB
Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois 60153. Electronic address: tpatel7@lumc.edu.
D000230:Adenocarcinoma / Q000378:metabolism*; D000302:Adrenal Cortex / Q000473:pathology*; D017209:Apoptosis; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D066246:ErbB Receptors / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000502:physiology*; D007680:Kidney Neoplasms / Q000378:metabolism*; D008565:Membrane Proteins; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism*; D012313:RNA / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000378:metabolism; D015533:Transcriptional Activation
D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D017978:Receptors, Growth Factor; C485561:SPRY2 protein, human; D012313:RNA; D050721:Proto-Oncogene Proteins c-cbl; D066246:ErbB Receptors; C067419:CBL protein, human