Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0032463 (polycythemia vera)
 3,374 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown that circulating progenitor cells in patients with polycythemia vera (PV) are hypersensitive to insulin-like growth factor I (IGF-I) with respect to erythroid burst formation in serum-free medium, and that this effect occurs through the IGF-I receptor. To investigate the molecular basis of this IGF-I hypersensitivity phenomenon, we examined tyrosine phosphorylation of the IGF-I receptor beta subunit in peripheral blood mononuclear cells (PBMNC) from eight PV patients and six normals. Cells were exposed to IGF-I at concentrations of 10(-8) and 10(-10) mol/L for 0, 1, 3, and 10 minutes, and then lysed. The IGF-I receptor beta subunit was immunoprecipitated, and the protein was resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotted with antiphosphotyrosine antibody (4G10). We found that, in the absence of exogenous IGF-I, there was a basal level of tyrosine phosphorylation of the IGF-I receptor beta subunit, and it was substantially greater in PV than in normal. At 10(-10) mol/L IGF-I in normals, no evidence of increased tyrosine phosphorylation was detected; however in PV, a pronounced increase in tyrosine phosphorylation was observed at both 10(-10) and 10(-8) mol/L IGF-I, and it occurred earlier and attained a higher level than in normal. In contrast, in PBMNC from three patients with erythrocytosis, no significant increase above normal was seen in either basal or induced tyrosine phosphorylation of the IGF-I receptor beta subunit. Thus, our findings show two distinctive features of the PV phenotype in PBMNC: (1) an increased basal tyrosine phosphorylation of the IGF-I receptor beta subunit, and (2) a hypersensitive and hyperresponsive receptor with respect to tyrosine phosphorylation. These features may influence the ability of the receptor to transmit a proliferative signal; thus, they may play a role in the pathogenesis of PV.
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PMID:Increased basal and induced tyrosine phosphorylation of the insulin-like growth factor I receptor beta subunit in circulating mononuclear cells of patients with polycythemia vera. 754

Previously, we found that, in the myeloproliferative disorder polycythemia vera (PV), circulating erythroid progenitor cells were hypersensitive to insulin-like growth factor I (IGF-I), an effect shown to occur through the IGF-I receptor. Also, in cells of PV patients, the IGF-I receptor was hyperphosphorylated on tyrosine residues under basal conditions, and its tyrosine phosphorylation in response to exogenous IGF-I was strongly augmented. Thus, because IGF-I appeared to play a role in the pathogenesis of PV, we wished to assess its level in the circulation of these patients. Normally, most of the circulating IGF-I is bound to specific high-affinity IGF binding proteins that can regulate its activity. We determined the circulating levels of IGF-I and two of its key binding proteins, IGFBP-1 and IGFBP-3. In two separate experiments, plasma samples from a total of 23 PV patients age- and sex-matched with 41 normal individuals were compared by radioimmunoassay. The levels of IGFBP-1 in patients with PV (37.80 +/- 4.33 microg/L) were more than fourfold higher than in normals (9.34 +/- 1.34 microg/L) or patients with secondary erythrocytosis (9.47 +/- 1.96 microg/L), whereas the plasma concentrations of IGFBP-3 and IGF-I in these patients were similar to those of normal subjects. Because circulating IGFBP-1 levels may be influenced by insulin, we measured the concentrations of insulin in the same samples. Our data showed that the elevation of circulating IGFBP-1 in PV could not be attributed to low levels of insulin in these patients. The substantial increase in concentration of IGFBP-1 was confirmed on ligand blots performed with (125)I-IGF-I. IGFBP-1 can be either inhibitory or stimulatory to the action of IGF-I under different conditions. We reasoned that if IGFBP-1 were stimulatory for erythropoiesis, an elevated IGFBP-1 level could help to explain the increased sensitivity to IGF-I observed in PV. If IGFBP-1 were inhibitory, it might suggest a compensatory mechanism in which a hyperphosphorylated IGF-I receptor in PV might induce a negative modulator of IGF-I action, in this case IGFBP-1. To distinguish between these two hypotheses, we titrated the effect of IGFBP-1 in the presence of IGF-I with respect to erythroid burst formation and found that IGFBP-1 was strikingly stimulatory. The elevated level of IGFBP-1 coupled with its ability to stimulate erythroid burst formation provide an attractive mechanism to account for the increased sensitivity of erythroid progenitor cells to IGF-I and the consequent overproduction of red blood cells characteristic of PV.
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PMID:Insulin-like growth factor binding protein-1 is elevated in patients with polycythemia vera and stimulates erythroid burst formation in vitro. 905 5