Synthesis of photoactivable probes for the study of glycosphingolipid-protein interactions

SYNTHESIS OF PHOTOACTIVABLE PROBES FOR THE STUDY OF GLYCOSPHINGOLIPID-PROTEIN INTERACTIONS Giuseppina Brasile,1 Federica Compostella,1 Laura Mauri,2Sandro Sonnino2 and Fiamma Ronchetti1 Dipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Universit\ue0 di Milano 1Via Saldini 50, 20133-Milano, Italy; 2Via Fratelli Cervi 93, 20190- Segrate (Milano), Italy E-mail:giuseppina.brasile@unimi.it It is widely accepted that glycosphingolipids (GSLs) at the level of the plasma membrane can affect the biological functions of protein molecules, such as cell surface receptors or transporters. The interactions between GSLs and proteins belonging to specific membrane microdomains, called lipid rafts, could be responsible for the modulation of the functional properties of membrane proteins participating in signal transduction. GSL-protein interactions can be investigated by cell photolabelling experiments using radioactive photoactivable GSLs, which yield, when illuminated, a very reactive intermediate that covalently binds to the molecules in the environment, i.e. proteins.1,2 In this context, we have designed a fatty acid probe with two nitrophenylazide photoactivable groups, one at position 2 and the other at the end of the acyl chain. The conjugation of the fatty acid to a radioactive sphingoglycolipid generates a species to be used for photolabelling experiments. In this way, the simultaneous identification of the proteins belonging to both the leaflets of the plasma membrane, the cytoplasmatic and the extracellular one, will be realized. Herein we describe a general synthetic strategy to obtain not commercially available \u3b1,\u3c9-diamino acids, the synthetic precursors of the labelled fatty acids, which we have applied to the synthesis of a C-18 derivative. Furthermore, it will be described the preparation of a photolabelled radioactive GSL as a case study. 1. Aureli M., Prioni S., Mauri L. Loberto N., Casellato R., Ciampa M.G., Chigorno V., Prinetti, A.; Sonnino S. J. Lipid Res. 2010, 51, 798-808 2. Mauri L., Prioni S., Loberto N., Chigorno V., Prinetti A., Sonnino S. Glycoconj. J. 2004, 20, 11-23