Brain spectrin (fodrin) interacts with phospholipids as revealed by intrinsic fluorescence quenching and monolayer experiments

Abstract

We demonstrate that phospholipid vesicles affect the intrinsic fluorescence of isolated brain spectrin. In the present studies we tested the effects of vesicles prepared from phosphatidylcholine (PtdCho) alone, in addition to vesicles containing PtdCho mixed with other phospholipids [phosphatidylethanolamine (PtdEtn) and phosphatidylserine] as well as from total lipid mixture extracted from brain membrane. The largest effect was observed with PtdEtn\PtdCho (3 : 2 molar ratio) vesicles ; the effect was markedly smaller when vesicles were prepared from egg yolk PtdCho alone. Brain spectrin injected into a subphase induced a substantial increase in the surface pressure of monolayers prepared from phospholipids. Results obtained with this technique indicated that the largest effect is again observed with monolayers prepared from a PtdEtn\PtdCho mixture. The greatest effect was observed when the monolayer contained 50-60 % PtdEtn in a

Actin-induced perturbation of PS lipid–cholesterol interaction: A possible mechanism of cytoskeleton-based regulation of membrane organization

“…Furthermore, there is growing evidence that phosphorylated derivatives of phosphatidylinositol such as phosphatidylinositol 4,5-bisphosphate (PIP2) may create membrane-cytoskeleton attachments by electrostatically binding to particular cytoskeleton-binding proteins such as MARCKS (Kwik et al, 2003). The possibility of direct cytoskeleton attachments to lipids has also been suggested because filamentous proteins of the cytoskeleton, including spectrin and filamin, possess lipid binding domains (Diakowski et al, 1999). Single particle tracking and laser tweezer experiments on mammalian cells have revealed that cytoskeleton-membrane attachments have a profound impact on membrane fluidity by forming fence-like diffusion obstacles, thereby compartmentalizing the plasma membrane Kusumi, 1994, 1995).…”

Mitoxantrone changes spectrin-aminophospholipid interactions

“…This lipid mixture was found by our previous studies to be optimal for interactions with spectrins, i.e., spectrin exerted the largest effect when monolayer contained 50 Á60% PE. Moreover, binding of both spectrin types to lipid mono-and bilayers proved sensitive to ankyrin inhibition suggesting its biological role [17,20]. The binding isotherm shows the saturable binding of mitoxantrone to liposomes to have an apparent equilibrium dissociation constant (K Dapp ) value of 13.3 )/10 (6 M and a maximal binding capacity of 10.6 nmol/mg of lipid.…”

Organization and Dynamics of Tryptophan Residues in Brain Spectrin: Novel Insight into Conformational Flexibility

“…Some of the tryptophan residues in brain spectrin are localized at or in the vicinity of hydrophobic patches which can bind ligands such as pyrene, fatty acids and phospholipids and cause quenching of tryptophan fluorescence [21,57]. The hydrophobic patches are useful in the interaction of brain spectrin with membranes.…”

“…This population of tryptophans is more likely to contribute to the observed REES of brain spectrin. In addition, many of these tryptophans are at or in the vicinity of hydrophobic patches in brain spectrin [57] which can bind hydrophobic ligands and the estimated apparent dielectric constant of the hydrophobic binding site(s) are low [21]. The low dielectric environment of these hydrophobic patches are generally characterized by restricted solvent molecules, rendering these regions suitable for displaying REES and other wavelength-selective effects [40,43,44; see later].…”