IL-4 protects cells from apoptosis via the insulin receptor substrate pathway and a second independent signaling pathway.
Although it has been known for some time that IL-4 protects cells from death via apoptosis, very little is known about the mechanism by which IL-4 exerts this effect. In this report, we have studied the molecular mechanisms of the IL-4-induced prevention of apoptosis in the 32D and B cell systems. IL-3 withdrawal has been shown to induce G1-arrest in 32D cells and subsequent death by apoptosis. We found that overexpression of IRS-1 protected 32D cells from death induced by IL-3 deprivation. IL-4 was able to protect 32D cells from apoptosis in the presence or absence of IRS-1. However, the protection from apoptosis of cells cultured in IL-4 was greater in the presence of IRS-1 and it reached levels comparable to those of cells cultured in IL-3. The IRS-1-dependent prevention of apoptosis is linked to the activation of PI 3'-kinase since wortmannin and LY294002, two inhibitors of PI 3'-K, partially inhibited the prevention of apoptosis mediated by IL-4 in 32D-IRS-1 cells after IL-3 withdrawal but not in 32D cells lacking IRS-1 expression. In addition, we found that the IRS/PI 3'-K pathway is, at least in part, responsible for the prevention of apoptosis by IL-4 in normal splenic B cell cultures. In spite of the ability of murine IL-4 to partially protect 32D cells lacking IRS-1 from apoptosis, human IL-4 was not able to prevent cell death in 32D-IRS-1 cells transfected with the human IL-4 receptor mutated in the insulin-lL-4 receptor motif (14R-motif) at amino acid 497 (Y497F). This mutation has previously been shown to abrogate the tyrosine phosphorylation of IRS-1 by human IL-4. These results demonstrate that IL-4 protects 32D cells from apoptosis by two different pathways, one of them mediated by IRS-1. In addition, these results suggest that the 14R-motif of the IL-4R is linked to both pathways.
Zamorano
J
J
Immunology Department, Jerome Holland Laboratories, American Red Cross, Rockville, MD 20855, USA.
Wang
H Y
HY
Wang
L M
LM
Pierce
J H
JH
Keegan
A D
AD
D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D055504:Insulin Receptor Substrate Proteins; D015847:Interleukin-4 / Q000235:genetics / Q000494:pharmacology*; D051379:Mice; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D018123:Receptors, Interleukin / Q000235:genetics / Q000378:metabolism; D019948:Receptors, Interleukin-4; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection
D015703:Antigens, CD; D017931:DNA Primers; D055504:Insulin Receptor Substrate Proteins; D015847:Interleukin-4; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D017346:Protein Serine-Threonine Kinases; D018123:Receptors, Interleukin; D019948:Receptors, Interleukin-4; D011994:Recombinant Proteins; D019893:Ribosomal Protein S6 Kinases; C526292:IRS1 protein, human; C526295:Irs1 protein, mouse