Cholecystokinin (CCK) is a satiety hormone produced by discrete enteroendocrine cells scattered among absorptive cells of the small intestine. CCK is released into blood following a meal; however, the mechanisms inducing hormone secretion are largely unknown. Ingested fat is the major stimulant of CCK secretion. We recently identified a novel member of the lipoprotein remnant receptor family known as immunoglobulin-like domain containing receptor 1 (ILDR1) in intestinal CCK cells and postulated that this receptor conveyed the signal for fat-stimulated CCK secretion. In the intestine, ILDR1 is expressed exclusively in CCK cells. Orogastric administration of fatty acids elevated blood levels of CCK in wild type but not ILDR1-deficient mice, although the CCK secretory response to trypsin inhibitor was retained. The uptake of fluorescently labeled lipoproteins in ILDR1-transfected CHO cells and release of CCK from isolated intestinal cells required a unique combination of fatty acid plus HDL. CCK secretion secondary to ILDR1 activation is associated with increased [Ca2+]i consistent with regulated hormone release. These findings demonstrate that ILDR1 regulates CCK release through a mechanism dependent on fatty acids and lipoproteins and that absorbed fatty acids regulate gastrointestinal hormone secretion.
Immunoglobulin-like domain containing receptor 1 mediates fat-stimulated cholecystokinin secretion.
Specimen part
View SamplesLevels of C/EBP are low in myeloid blast crisis (BC) of chronic myelogenous leukemia (CML) and its expression in p210BCR/ABL-expressing hematopoietic cells induces granulocytic differentiation, inhibits proliferation and suppresses leukemogenesis. To assess the mechanisms involved in these effects, C/EBP targets were identified by microarray analyses. Upon C/EBP activation, expression of c-Myb and GATA-2 was repressed in 32D-BCR/ABL, K562 and CML-BC primary cells but only c-Myb levels decreased slightly in CD34+ normal progenitors. The role of these two genes for the biological effects of C/EBP was assessed by perturbing their expression in K562 cells. Expression of c-Myb blocked the proliferation inhibition and differentiation-inducing effects of C/EBP while c-Myb siRNA treatment enhanced C/EBP-mediated proliferation inhibition and induced changes in gene expression indicative of monocytic differentiation. GATA-2 expression suppressed the proliferation inhibitory effect of C/EBP but blocked in part the effect on differentiation; GATA-2 siRNA treatment had no effects on C/EBP induction of differentiation but inhibited proliferation of K562 cells, alone or upon C/EBP activation. In summary, the effects of C/EBP in p210BCR/ABL -expressing cells depend, in part, on transcriptional repression of c-Myb and GATA-2. Since perturbation of c-Myb and GATA-2 expression has non identical consequences for proliferation and differentiation of K562 cells, the effects of C/EBP appear to involve different transcription-regulated targets.
Transcriptional repression of c-Myb and GATA-2 is involved in the biologic effects of C/EBPalpha in p210BCR/ABL-expressing cells.
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View SamplesExpression profiling of cultured HL-1 cardiomyocytes subjected to hypoxia for 8 hours.
The VLDL receptor promotes lipotoxicity and increases mortality in mice following an acute myocardial infarction.
Cell line
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