Effects exerted by diacylglycerols on the surface expression of the nicotinic receptor in CHO cells”

PEDICONI MARÍA FILOMENA; VALLÉS ANA SOFIA; BARRANTES FRANCISCO JOSÉ

Buzios, Brasil

Congreso; I Congresso IBRO/LARC de Neurociencias de América Latina, Caribe y Península Ibérica (Neurolatam).; 2008

Ibro/Larc

Results from our laboratory indicated that sphingomyelin (SM) and ceramides have a key role in the trafficking of nicotinic receptor (AChR) to the cellular membrane (1,2).  We have postulated that SM formation as well as diacylglycerols (DAG), a coproduct in the biosynthesis of SM, are significantly important in receptor trafficking.  Objetives: in the present work we studied the possible modulatory effects of exogenous DAGs and phorbol ester on the trafficking of AChR in CHO-K1/A5 cells Methods: ligand binding assays and fluorescence microscopy experiments. Results: we determined using the specific ligand 125I a-bungarotoxin, that long chain DAG (palmitoyl-oleoyl glycerol) exogenously supplied in concentrations of 200 and 400 mM by 3 h, significantly increases the surface expression of AChR to 115±2 and 130±8% respectively. The higher amount of the receptor detected in treated cells respect to control ones occurs without change in its affinity for the ligand (20 nM).  The analysis of receptor distribution in cells treated with 300 mM of DAG reveals an increase on the total amount of the AChR mainly detected as consequence of the increase at the cellular membrane.  In addition, short chain DAG (dioctanoyl glycerol) induces a higher increase (180%) of the AChR detected at the plasma membrane after 30 min of treatment.  Experiments conducted in the presence of a phorbol ester, allowed us to determine that the DAG analog was more effective in increasing the AChR expression at the plasma membrane than long chain diacylglycerol, affecting also the affinity of the receptor for a-bungarotoxin.   Conclusion:  DAG positively modulates AChR trafficking to the plasmalemma. References: 1- J. Neurochem. 2007: 101, 1072; 2- Biochim. Biophys. Acta, 1778:917, 2008