engleski

Redistribution of gangliosides accompanies thermally induced Na+, K+ -ATPase activity alternation and submembrane localisation in mouse brain

We report a phenomenon of surprising alternation in Na+, K+-ATPase (NKA) activity following an increasing number of freeze-thaw cycles which we employed as a means for remodelling the membrane. Utilizing an array of methods including spectrophotometry to determine NKA activity, Western blotting, membrane subfractionation, lipid raft isolation, purification of gangliosides derived from different membrane subcompartments, and immunoblotting, we demonstrated that: (a) modulation of membrane integrity by freeze-thaw manipulation leads to changes in NKA localization to distinct membrane micro-regions and consequent change in NKA activity ; (b) there is a concerted shift of gangliosides and NKA within the membrane itself, where particular ganglioside species mirror the changes in NKA activity, and other reflect NKA protein distribution.The experimental data support the hypothesis that specific ganglioside species aid NKA positioning within the membrane and therefore optimal function of the pump. Although gangliosides are not the sole factor affecting NKA activity, we believe we have demonstrated that they should be taken into serious consideration when studying NKA activity. Considering that NKA has multiple roles in signaling pathways in addition to being an electrogenic pump, and that the consequences of impaired NKA function are extensive and severe, the possibility to modulate NKA pumping and signaling properties is highly attractive. Therefore, investigating gangliosides as modulators of NKA activity represents a new prospect in the research of NKA and NKA-linked disorders.

lipid rafts ; glycosphingolipids ; sodium pump ; enzyme activity

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