Receptor-Mediated Transcytosis of Leptin through Human Intestinal Cells In Vitro

Figure 3

Presence of leptin receptors in Caco-2/15 cells. (a) Leptin receptor long (219.1) and short (219.3) isoform mRNAs are present in Caco-2/15 cells as revealed by RT-PCR analysis. (b) In three different experiments (C1, C2, C3), Western blots demonstrate the presence of the long (219.1) (120 kDa) and short (219.3) (100 kDa) isoforms of the leptin receptor, as well as that of the soluble receptor (OBRs) (80 kDa). The isoform 219.2 was not found. Confocal microscopy carried out on cell monolayer displays intense green staining for the leptin receptor on the apical pole of the cells (c1) and a more granulated and dispersed staining on more central regions of the same cells (c2). (d1) Immunogold electron microscopy confirms the presence of the leptin receptor on the apical plasma membrane particularly at the level of the microvilli (mv) and on the limiting membrane of endocytotic vesicles where gold particles are easily detected (e). (d2) Control of specificity: cell monolayers were incubated without the primary antibody showing absence of labelling by gold particles.