?Insulin resistance augments nicotinic acetylcholine receptor (nAChR) internalization and inhibits its cell-surface expression upon acute insulin treatment?

FRANCISCO J. BARRANTES; ANA PAULA GARCÍA; EUGENIA PÉREZ

Congreso; XXXIV Congreso Anual de la Sociedad Argentina de Investigación en Neurociencias; 2019

Sociedad Argentina de Investigación en Neurociencias

The levels of nAChR in the plasma membrane (PM) depends on trafficking processes that involve the actin cytoskeleton (AC). In addition, the AC is required for the insulin stimulation of glucose uptake. Here we assess whether exposure to a sustained hyperinsulinemia-like milieu mimicking insulin resistance (IR) affects the stability of the nAChR in the PM. For this, CHO-K1/A5 cells, a clonal cell line heterologously expressing adult-type muscle nAChR, were incubated with 10nM insulin for 19-22h (long insulin) to develop IR. Effects of insulin on nAChR PM levels, ligand-mediated internalization (which depends on AC integrity), and actin filament (AF) morphology were assessed using specific fluorescence probes and immunofluorescence microscopy. IR was made apparent after long insulin by the lack of insulin responsiveness to glucose uptake. Acute insulin application (10, 25 and 100nM) produced a significant and dose-dependent increase of nAChR levels in the PM, already evident at 30min and more pronounced at 60min. These effects were accompanied by an increase in the number of AFs. When cells were subjected to IR, the acute effect of insulin on nAChR PM levels was abolished and a concomitant decrease of AFs was observed, together with a significant increase in ligand-mediated nAChR internalization. In conclusion, insulin can affect the levels of expression of the nAChR in the plasmalemma and IR disrupts the endocytic dynamics of this receptor, possibly by altering the AC status.1)Kumari S, Borroni V, Chaudhry A, Chanda B, Massol R, Mayor S and Barrantes FJ (2008). J. Cell. Biol. 181: 1179-1193.2)Borroni, M.V. and Barrantes, F.J. (2011). J. Biol. Chem. 286, 17122-17132.