RESUMO
ApoB-100 and apoB-48 are major components of chylomicrons, very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL). The two proteins are generated from a single apoB mRNA by apoB mRNA editing which induces an in-frame stop codon in apoB mRNA. Apolipoprotein B (apoB) mRNA editing is an important determinant of the proportion of full-length (apoB-100) and truncated (apoB-48) proteins in total apoB metabolism. Calcium is involved in the regulation of secretion and synthesis of VLDL and apoB. In this paper, we demonstrate for the first time that the amount of edited apoB mRNA in the cultured cells Caco-2 and McA7777 is markedly increased by calcium. Increasing extracellular calcium concentration, calcium ionophore (A23187 and ionomycin) treatment, and depleting calcium stores and raising cytoplasmic calcium concentration by thapsigargin increase apoB mRNA editing up to threefold in a dose dependent manner. Calcium has no direct stimulative effect on apoB mRNA editing in an in vitro editing system. The editing increase by extracellular calcium is not related to alterations of APOBEC-1 mRNA expression. These data suggest that calcium is not only involved in the regulation of apolipoprotein metabolism but also apoB mRNA editing.
Assuntos
Apolipoproteínas B/genética , Cálcio/farmacologia , Edição de RNA/efeitos dos fármacos , Desaminase APOBEC-1 , Animais , Células CACO-2 , Calcimicina/farmacologia , Cálcio/metabolismo , Citidina Desaminase/metabolismo , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Humanos , Ionomicina/farmacologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Tapsigargina/farmacologia , Fatores de Tempo , Células Tumorais CultivadasRESUMO
This study examined the strength of the relationship between computerized and paper-and-pencil noncognitive selection measures. The tendency to engage in response distortion across these 2 modes was also assessed. The raw cross-mode correlations exceeded .90 for all of the substantive selection scales studied. Indeed, latent cross-mode correlations were estimated to be 1.0 for all of these scales. Mean score comparisons of 1 of the response distortion measures (i.e., the Balanced Inventory of Desirable Responding) suggested that response distortion in the computer-administration mode was significantly greater than response distortion observed with a paper-and-pencil format. However, administration mode did not influence scores on another measure of direct response distortion or any of the substantive selection measures administered.
