Alterations in membranemediated functions and signals

Alterations in the function of membrane proteins

Changes in plasma membrane structural characteristics can change the activity of proteins that serve as ion channels, adhesion molecules, transporters, receptors, signal transducers or enzymes (Stubbs and Smith, 1984; Clandinin et al., 1991). Many membrane-associated proteins in immune cells have been shown to be modulated by membrane lipid changes. For example, feeding 5% w/w long-chain n-3 PUFAs to rats resulted in a higher proportion of T- and B-cells and macrophages expressing the transferrin receptor (CD71) after stimulation with mitogen (Robinson and Field, 1998), although feeding a higher amount of fish oil did not induce this effect (Yaqoob et al., 1994b). The binding of cytokines to their receptor has been reported to be altered with changes in membrane composition (Grimble and Tappia, 1995). Additionally, the expression of several cell surface molecules was reported to be altered after fish oil feeding (Sanderson et al., 1995; Hughes et al., 1996; Robinson and Field, 1998; Sanderson and Calder, 1998a; Field et al., 2000; Hughes and Pinder, 2000; Robinson et al., 2001). Many of these molecules are involved in the co-stimulation processes necessary for lymphocyte activation, and some of the effects are suggestive of improved cell-mediated immune function.

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