Raphaël Scharfmann1, A. Tazi1, Miche Polak1, Christina Kanaka1, Paul Czernichow1
1Department of Pediatric Endocrinology, Hopital R. Debre Paris, France
Tóm tắt
Previous data demonstrated that one rat insulinoma cell line, RINm5F cells, which is a rat β-cell line derived from a pancreatic tumor, express mRNA coding for both the low- and the high-affinity nerve growth factor receptors. Goals of this study were to extend our data to other β-cell lines and fetal islets in primary culture and to study further the binding characteristics of nerve growth factor receptors on β-cells. Northern blot analysis revealed that not only a panel of endocrine β-cell lines (RINm5F, INS-1, β-TC3) but also fetal rat islets in primary culture express mRNA coding for trk-A, which has been proposed to be the neuronal high-affinity nerve growth factor receptors. Reverse polymerase chain reaction followed by sequencing revealed that the sequence of trk-A receptor in RINm5F cells is identical to that of trk-A expressed in PC12 cells. The expression of the low-affinity nerve growth factor receptor was examined by Northern blot analysis that showed low-affinity nerve growth factor receptor to be expressed in RINm5F and INS-1 cell lines, in fetal rat islets in primary culture, but not in β-TC3-cells. Binding experiments revealed the presence of low- and high-affinity nerve growth factor binding sites, identical to those described for PC12 cells, on RINm5F and INS-1 cells and only high-affinity binding sites on β-TC3 cells. Exposure of all three β-cell lines to nerve growth factor increased NGFI-A and c-fos mRNA steady-state levels, showing that these receptors are functional. These data demonstrate that the entire machinery required for nerve growth factor action is present in β-cells in culture.
