Deletion of the pleckstrin and phosphotyrosine binding domains of insulin receptor substrate-2 does not impair its ability to regulate cell proliferation in myeloid cells.
32D IGF-I receptor (IR) cells are IL-3-dependent myeloid cells that can be induced to differentiate into granulocytes by IGF-I. Like the parental 32D cells, 32D IGF-IR cells do not express the insulin receptor substrate (IRS)-1 or IRS-2. We investigated the effect of ectopic expression of IRS-2 in 32D IGF-IR cells. Expression in these cells of a wild-type IRS-2 inhibits IGF-I-induced differentiation, and the cells grow indefinitely in the absence of IL-3. We also investigated the effect of a mutant IRS-2 lacking both the pleckstrin (PH) and the phosphotyrosine-binding (PTB) domains, which are known to bind to the IR. The partial differentialPHPTB IRS-2 is fully as capable as the wild-type IRS-2 (and wild-type IRS-1) to stimulate the growth and inhibit the differentiation of 32D IGF-IR cells. In contrast, an IRS-1 protein lacking the same PH and PTB domains is completely inactive in blocking differentiation and stimulating IL-3-independent growth of 32D IGF-IR cells. The partial differentialPHPTB IRS-2 protein is dependent for its effect on an activated IGF-IR, is cytoplasmic, binds to the beta-subunit of the IGF-IR, and requires for its action the presence of phosphatidylinositol 3-kinase binding sequences. These experiments show that the PH and PTB domains of IRS-2 (but not IRS-1) are dispensable for the IGF-I/IRS-2-mediated growth of 32D myeloid cells. Our results also indicate that IRS-2 (either wild type or partial differentialPHPTB) is capable of inhibiting the differentiation of 32D cells.
Sun
Hongzhi
H
Kimmel Cancer Center, Thomas Jefferson University, 233 South 10th Street, 624 BLSB, Philadelphia, Pennsylvania 19107, USA.
Baserga
Renato
R
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D001798:Blood Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D017353:Gene Deletion; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007377:Interleukin-3 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D022423:Myeloid Cells / Q000166:cytology* / Q000502:physiology*; D009195:Peroxidase / Q000235:genetics; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D001798:Blood Proteins; D055504:Insulin Receptor Substrate Proteins; D007377:Interleukin-3; D047908:Intracellular Signaling Peptides and Proteins; C526295:Irs1 protein, mouse; C526298:Irs2 protein, mouse; D010750:Phosphoproteins; D035463:Pol1 Transcription Initiation Complex Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C039077:platelet protein P47; C063844:transcription factor UBF; D019000:Phosphotyrosine; D007334:Insulin-Like Growth Factor I; D009195:Peroxidase; D017526:Receptor, IGF Type 1