Cross down-regulation of leptin and insulin receptor expression and signalling in a human neuronal cell line

• DOI: 10.1042/bj20041621
• Publication Date: 2005-06-07T09:42:39Z
• Authors: Yacir BENOMAR; Anne-France ROY; Alain AUBOURG; Jean DJIANE; Mohammed TAOUIS
• Keywords: MESH: Signal Transduction; Leptin; 0301 basic medicine; [SDV.NEU.NB]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology; [SDV]Life Sciences [q-bio]; MESH: Neurons; [SDV.NEU.PC] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Psychology and behavior; MESH: Down-Regulation; Phosphatidylinositol 3-Kinases; MESH: Receptors; Insulin; MESH: Animals; MESH: Receptors, Cell Surface; Neurons; Tumor; [SDV.NEU.PC]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Psychology and behavior; Intracellular Signaling Peptides and Proteins; [SDV.NEU.SC]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Cognitive Sciences; MESH: Protein Subunits; MESH: Insulin Receptor Substrate Proteins; [SDV] Life Sciences [q-bio]; Cell Surface; Receptors, Leptin; Protein Binding; Signal Transduction; EXPRESSION; 571; MESH: Cell Line, Tumor; MESH: Receptor, Insulin; MESH: Sheep; Down-Regulation; Receptors, Cell Surface; MESH: Receptors, Leptin; MESH: Insulin; [INFO] Computer Science [cs]; MESH: Phosphoproteins; MESH: Gene Expression Profiling; 03 medical and health sciences; MESH: Intracellular Signaling Peptides and Proteins; Cell Line, Tumor; MESH: Protein Binding; Animals; Humans; Immunoprecipitation; [INFO]Computer Science [cs]; MESH: Tretinoin; MESH: Humans; Sheep; MESH: Immunoprecipitation; Gene Expression Profiling; MESH: Receptor; [SDV.NEU.NB] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology; MESH: Leptin; Phosphoproteins; Receptor, Insulin; MESH: Cell Line; Protein Subunits; MESH: Phosphatidylinositol 3-Kinases; Insulin Receptor Substrate Proteins; [SDV.NEU.SC] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Cognitive Sciences

Leptin and insulin are major signals to the hypothalamus to regulate energy homoeostasis and body adiposity. IR (insulin receptors) and leptin receptors (long isoform, ObRb) share a number of signalling cascades, such as JAK2/STAT-3 (Janus kinase 2/signal transduction and activator of transcription 3) and PI3K (phosphoinositide 3-kinase); the cross-talk between IR and ObRb have been described previously in non-neuronal cells. Differentiated human neuroblastoma (SH-SY5Y) cells express endogenous ObR and IR, and respond to leptin and insulin with stimulation of STAT-3 and MAPK (mitogen-activated protein kinase) phosphorylation, and PI3K activity. Insulin or leptin pre-treatment of SH-SY5Y cells increased basal STAT-3 phosphorylation, but abolished the acute effect of these hormones, and, interestingly, leptin pre-treatment abolished insulin effect and vice versa. Similar results were obtained for MAPK phosphorylation, but leptin or insulin pre-treatment did not completely abolish the acute effect of insulin or leptin. We have also showed that insulin and leptin are able to activate PI3K through IRS-1 (insulin receptor substrate 1) and IRS-2 respectively. Furthermore, leptin or insulin pre-treatment increased basal PI3K activity and IRS-1 or IRS-2 association with p85 and abolished acute insulin or leptin effect, in addition to the down-regulation of IRS-1 and IRS-2. Finally, insulin pre-treatment reduced leptin binding by approx. 60%, and leptin pre-treatment reduced the expression of insulin receptor by 40% in SH-SY5Y cells, which most likely accounts for the cross down-regulation of leptin and insulin receptors. These results provide evidence to suggest cross down-regulation of leptin and insulin receptors at both receptor and downstream signalling levels. This finding may contribute to the understanding of the complex relationship between leptin resistance and insulin resistance at the neuronal level.