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.
Kimmel Cancer Center, Thomas Jefferson University, 233 South 10th Street, 624 BLSB, Philadelphia, Pennsylvania 19107, USA.
Hongzhi
H
Sun
Renato
R
Baserga
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