Gangliosides affect membrane-channel activities dependent on ambient temperature

1. The functional properties of biological membranes depend on their molecu lar composition. In regard to this, charged glycosphingolipids play an outs tanding role in the functional adaptation of membranes to different tempera tures. 2. In order to shed some light on the respective functional properties of c omplex membraneous glycosphingolipids, the effects of altered temperatures (5-40 degrees C) on planar lipid bilayers made from diphytanoylphosphalidyl choline (DPPC) and alamethicin as an ion channel was analyzed in the presen ce of either a sialoglycosphingolipid (less polar disialoganglioside GD1a o r highly polar tetrasialoganglioside GQ1b) or phosphatidylserine (PS; as co ntrol). 3. Different to the control bilayers made from DPPC or DPPC + PS, the bilay ers containing gangliosides had specific maxima in alamethicin conductance and stabile life times. Changes in pore-state conductances indicate structu ral effects based on an interaction of the large (negatively charged) gangl ioside headgroups with the alamethicin pores. 4. The results concerning open time and closed time of channels seem to be based on the gangliosides changing the viscosity of the bilayer and possibl y introducing phase transitions. 5. Thus, the findings suggest that gangliosides (1) directly affect channel molecules via their headgroups and (2) may additionally affect the fluidit y of membranes in order to maintain membrane homeoviscosity in areas surrou nding ion channels independent from the environmental temperature. 6. The effects of gangliosides may be of special interest in describing the ability of neuronal adaptation of vertebrates to temperature and more gene ral regarding the functional adaptation of neurons.