Role of lipid-induced changes in plasma membrane in the biophysical shunt theory of psychopathology

Nutrition and immune system: certain fatty acids differently modify membrane composition and consequently kinetics of KV1.3 channels of human peripheral lymphocytes

Potassium (K(+)) channels of human peripheral lymphocytes play a considerable role in the signalling processes required for immune responses. Modification of the fatty acid composition of the membrane influences the functions of various membrane enzymes and ion channels. We set out to establish how the incorporation of fatty acids with different carbon chain lengths and degrees of unsaturation into the cell membrane influences the function of K(V)1.3 channels of lymphocytes, thereby potentially modifying the immune responses of the cells. The incorporation of the fatty acids into the cell membrane was monitored by gas chromatography. Whole-cell patch-clamp experiments demonstrated that the polyunsaturated linoleic acid, arachidonic acid and docosahexaenoic acid all decreased the activation and inactivation time constants of the K(V)1.3 channels, but did not affect the voltage-dependence of steady-state activation and steady-state inactivation of the channels. Treatment with the saturated palmitic acid, stearic acid and the monounsaturated oleic acid did not result in significant changes in the biophysical parameters of K(V)1.3 gating studied. We conclude that the incorporation of fatty acids unsaturated to different degrees into the cell membrane of lymphocytes influenced the rate of gating transitions but not the equilibrium distribution of the channels between different states. This effect depended on the degree of unsaturation and the chain length of the fatty acids: no effects of saturated and monounsaturated fatty acids (16:0, 18:0 and 18:1) were observed whereas treatment with polyunsaturated fatty acids (18:2, 20:4 and 22:6) resulted in significant changes in the channel kinetics.

Amyloid beta peptide membrane perturbation is the basis for its biological effects

Experimental studies have indicated that the mechanisms offered for explaining the neurotoxicity of amyloid beta peptide (AbetaP) are diverse, and include altered enzyme activities, disrupted calcium homeostasis, and increased free radical formation. AbetaP appears to interact at the cell membrane with a multitude of receptor sites and also inserts physically into the membrane matrix. This membrane insertion affects the membrane fluidity and potentially influences the function of resident membrane proteins. We propose a unifying hypothesis to explain the experimental observations of the diverse cellular responses to AbetaP. The indiscriminate physical insertion of AbetaP into the cell membrane unspecifically activates a host of membrane processes by perturbation of the membrane proteins. This recurrent activation of membrane processes eventually culminates in neuronal cell death. We recommend that successful therapeutic interventions should be directed at reducing or preventing the interaction of AbetaP with neuronal cell membranes.