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An investigation whether phospholipid transfer protein (PLTP) and cholesteryl ester transfer protein (CETP) are present in human tear fluid is conducted, in order to gain insight into the formation of tear film. The results suggest that PLTP may play role in the formation of the tear film by supporting phospholipid transfer.

The physicochemical properties of sphingolipids in a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) matrix were investigated. To this end, the behaviors of two chemically well-defined sphingolipids, N-palmitoyl-sphingomyelin and the corresponding ceramide, were compared. Experimental results showed that the enzymatic generation of ceramide from sphingomyelin stimulates microdomain formation in LUVs, although the reorganization of ceramide into microdomains within the bilayer took a significantly longer time.

A synthetic peptide, corresponding to 1 to 42 amino acid residue of amyloid beta-peptide (A-Beta(sub 1-42)), enhances the hydrolysis of the pyrene-labeled acidic phospholipid analog 1-palmitoyl-2-((pyren-1-yl))hexanoyl-sn-glycero-3-phosphoglycerol by porcine pancreatic phospholipase A(sub 2). Ca2+, at higher concentrations, abolishes the enhancing effect of A-Beta(sub 1-42), which is found in senile plaques in Alzheimer's disease (AD). Brain samples of AD patients show decreased levels of phosphatidylcholine. Activation of lipolytic enzyme by amyloid beta peptide indicates a direct involvement of the peptide in neuronal cell death in AD afflicted brain tissue.

Biochemical studies are conducted to identify proteins in retinal cell extracts that interact with RP2 in order to define the role of RP2 in the retina and X-linked retinitis pigmentosa (XLRP). The studies have shown that RP2, in addition to serving as a regulator of ADP ribosylation factor-like 3 (Arl3), has interacted with N-ethylmaleimide sensitive factor (NSF) and the complex has played a vital role in membrane protein trafficking in photoreceptors and other cells of the retina.

The interfacial properties of phospholipid transfer protein (PLTP) are studied using Langmuir phospholipid monolayers and asymmetrical flow field--flow fractionation (AsFIFFF) to follow the transfer of [super 14]C-labeled phospholipids and {[super 35]S}PLTP between lipid vesicles and high-density lipoprotein particles. It is observed that high activity-PLTP (HA-PLTP) can transfer lipids by a shuttle mechanism and phospholipid transfer can take place in the absence of formation of ternary complex between PLTP, acceptor and donor particles.

In circulation the phospholipid transfer protein (PLTP) facilitates the transfer of phospholipid-rich surface components from postlipolytic chylomicrons and very low density lipoproteins (VLDL) to HDL and thereby regulates plasma HDL levels. To study the molecular mechanisms involved in PLTP-mediated lipid transfer, we studied the interfacial properties of PLTP using Langmuir phospholipid monolayers and asymmetrical flow field-flow fractionation (AsFlFFF) to follow the transfer of 14C-labeled phospholipids and [35S]PLTP between lipid vesicles and HDL particles. The AsFlFFF method was also used to determine the sizes of spherical and discoidal HDL particles and small unilamellar lipid vesicles. In Langmuir monolayer studies high-activity (HA) and low-activity (LA) forms of PLTP associated with fluid phosphatidylcholine monolayers spread at the air/buffer interphase. Both forms also mediated desorption of [14C]dipalmitoylphosphatidylcholine (DPPC) from the phospholipid monolayer into the buffer phase, even when it contained no physiological acceptor such as HDL. After the addition of HDL3 to the buffer, HA-PLTP caused enhanced lipid transfer to them. The particle diameter of HA-PLTP was and that of HDL3 ~8 nm as determined by AsFlFFF analysis. Using this method, it could be demonstrated that in the presence of HA-PLTP, but not LA-FLIP, [14C]DPPC was transferred from small unilamellar vesicles (SUV) to acceptor HDL3 molecules. Concomitantly, [35S]-HA-PLTP was transferred from the donor to acceptor, and this transfer was not observed for its low-activity counterpart. These observations suggest that HA-PLTP is capable of transferring lipids by a shuttle mechanism and that formation of a ternary complex between PLTP, acceptor, and donor particles is not necessary for phospholipid transfer. [ABSTRACT FROM AUTHOR]

Reports that amyloid beta-peptides (ABP) are centrally involved in pathogenesis of Alzheimer's disease. Correlation of disease severity with extent of ABP accumulation; Composition of ABP found in cerebral amyloid deposits; Variations of C-terminal residues in series of peptides.