Differences in reactivity of antibodies to active versus inactive PLTP significantly impacts PLTP measurement

Murdoch, Susan J.; Wolfbauer, Gertrud; Kennedy, Hal; Marcovina, Santica M.; Carr, Maria; Albers, John J.

doi:10.1016/s0022-2275(20)30170-x

Cited by 30 publications

(4 citation statements)

References 21 publications

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“…The increase in PLTP-mediated phospholipid transfer activity in inflammation may represent (1) a protective mechanism against the deleterious effects of LPS in endotoxemia by facilitating the transfer of LPS to HDL and thereby neutralizing its activity and (2) the facilitation of the transfer of phospholipid and alpha tocopherol to tissues needed for the protection or regeneration of cellular membranes such as those from vascular endothelial cells, that may be targets of the activated components of the complement and coagulation systems during inflammation ,, . The ability of PLTP to transfer phospholipids appears to depend, in part, on the size of the PLTP complexes as large PLTP complexes (520 ± 120 kDa; 12 to >17 nm) contain an inactive form of PLTP, while complexes associated with an active form of PLTP are smaller (160 ± 40 kDa) (7.6−12 nm) , . It is not known if the larger inactive PLTP complexes have more lipids than the smaller active PLTP complexes as would be expected if these complexes possess a structure similar to HDL particles.…”

Section: Discussionmentioning

confidence: 99%

“…We also prepared Mab4, a monoclonal antibody to PLTP that recognizes a population of plasma PLTP that is unable to transfer phospholipid from liposomes to HDL (6). Mab4 was produced by injecting pristine primed Balb/c mice with the Mab4 hybridoma cells, and the antibody was purified from the ascites with fast-flow protein A-Sepharose (GE Life Sciences).…”

Section: Methodsmentioning

confidence: 99%

“…PLTP associates with apoA-I and apoE , , as well as with several unidentified proteins . Two forms of PLTP have been detected in human plasma: an “active” form that transfers phosphatidylcholine from phospholipid vesicles to high-density lipoproteins (HDL) and an “inactive” form that lacks this capability − . The apparent molecular mass of the “active” form is similar to that of small HDL particles (∼160 kDa), while the inactive complexes appear to be much larger (apparent MW ∼520 kDa) − .…”

mentioning

confidence: 99%

“…Two forms of PLTP have been detected in human plasma: an “active” form that transfers phosphatidylcholine from phospholipid vesicles to high-density lipoproteins (HDL) and an “inactive” form that lacks this capability − . The apparent molecular mass of the “active” form is similar to that of small HDL particles (∼160 kDa), while the inactive complexes appear to be much larger (apparent MW ∼520 kDa) − . However, the plasma fraction showing the greatest PLTP activity has a density of 1.24 g/mL, which is significantly greater than that of HDL (1.063−1.21 g/mL).…”

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confidence: 99%

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Phospholipid Transfer Protein in Human Plasma Associates with Proteins Linked to Immunity and Inflammation

et al. 2010

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Phospholipid transfer protein (PLTP), which associates with apolipoprotein A-I (the major HDL protein) plays a key role in lipoprotein remodeling. Because its level in plasma increases during acute inflammation, it may also play previously unsuspected roles in the innate immune system. To gain further insight into its potential physiological functions, we isolated complexes containing PLTP from plasma by immunoaffinity chromatography, and determined their composition. Shotgun proteomics revealed that only 6 of the 24 proteins detected in the complexes were apolipoproteins. The most abundant proteins were clusterin (apoJ), PLTP itself, coagulation factors, complement factors, and apoA-I. Remarkably, 20 of the 24 proteins had known proteinprotein interactions. Biochemical studies confirmed two previously established interactions and identified 5 new ones between PLTP and proteins. Moreover, clusterin, apoA-I, and apoE preserved the lipid-transfer activity of recombinant PLTP in the absence of lipid, indicating that these interactions may have functional significance. Unexpectedly, lipids accounted for only 3% of the mass of the PLTP complexes. Collectively, our observations indicate that PLTP in human plasma resides on lipid-poor complexes dominated by clusterin and proteins implicated in host defense and inflammation. They further suggest that protein-protein interactions drive the formation of PLTP complexes in plasma.Phospholipid transfer protein (PLTP) is an 80-kDa glycoprotein that binds phospholipids and facilitates their transfer between lipoproteins in plasma. It is expressed by macrophages and many other tissues (1,2). PLTP associates with apoA-I and apoE (3,4), as well as with several unidentified proteins (4). Two forms of PLTP have been detected in human plasma: an "active" form that transfers phosphatidylcholine from phospholipid vesicles to high density lipoproteins (HDL), and an "inactive" form that lacks this capability (4-6). The apparent molecular weight of the "active" form is similar to that of small HDL particles (~160 kDa), while the inactive complexes appear to be much larger (apparent MW ~520 kDa) (4-6). However, the plasma fraction showing the greatest PLTP activity has a density † This study was supported by grants (H030086, HL086798) from the National Institutes of Health. TV was supported by a Pilot and Feasibility Award from the Diabetes and Endocrinology Research Center (NIH 5 P30 DK17047), and Scientist Development Grant Award from American Heart Association 0830231N. Mass spectrometry experiments were supported by the Mass Spectrometry Resource, Department of Medicine, and the Mass Spectrometry Core, Diabetes and Endocrinology Research Center, University of Washington. * To whom correspondence should be addressed: Northwest Lipid Metabolism and Diabetes Research Laboratories, Department of Medicine, University of Washington, 401 Queen Anne Avenue North, Seattle, 685-3279. jja@u.washington.edu. ∥ These authors contributed equally to the work. NIH Public Access Author Manusc...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Phospholipid Transfer Protein in Human Plasma Associates with Proteins Linked to Immunity and Inflammation

et al. 2010

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Human Plasma Phospholipid Transfer Protein (PLTP) – Structural and Functional Features

Siggins¹,

Rye²,

Olkkonen³

et al. 2007

High‐Density Lipoproteins

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Reduced CSF PLTP activity in Alzheimer's disease and other neurologic diseases; PLTP induces ApoE secretion in primary human astrocytes in vitro

Vuletic

Peskind

Marcovina

et al. 2005

J of Neuroscience Research

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Phospholipid transfer protein (PLTP) plays a pivotal role in cellular lipid efflux and modulation of lipoprotein metabolism. PLTP is distributed widely in the central nervous system (CNS), is synthesized by glia and neurons, and is active in cerebrospinal fluid (CSF). The aims of this study were to test the hypothesis that patients with Alzheimer's disease (AD) have altered PLTP-mediated phospholipid transfer activity in CSF, and to examine the potential relationship between PLTP activity and apolipoprotein E (apoE) levels in CSF. We assessed PLTP activity and apoE concentration in CSF of patients with probable AD (n = 50), multiple sclerosis (MS; n = 9), other neurologic diseases (n = 21), and neurologically healthy controls (n = 40). PLTP activity in AD was reduced compared to that in controls (P < 0.001), with approximately half of the AD patients with PLTP activity values below all controls. Patients with MS had lower PLTP activity than AD patients (P < 0.001). PLTP activity was highly correlated with PLTP mass, as estimated by Western blot (r = 0.006; P < 0.01). CSF PLTP activity positively correlated with apoE concentration in AD (R = 0.435; P = 0.002) and controls (R = 0.456; P = 0.003). Anti-apoE immunoaffinity chromatography and Western blot analyses indicated that some CSF PLTP is associated with apoE-containing lipoproteins. Exogenous addition of recombinant PLTP to primary human astrocytes significantly increased apoE secretion to the conditioned medium. The findings of reduced PLTP activity in AD CSF, and the observation that PLTP can influence apoE secretion in astrocytes suggest a potential link between alterations in the brain lipid metabolism and AD pathogenesis.

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Differences in reactivity of antibodies to active versus inactive PLTP significantly impacts PLTP measurement

Cited by 30 publications

References 21 publications

Phospholipid Transfer Protein in Human Plasma Associates with Proteins Linked to Immunity and Inflammation

Phospholipid Transfer Protein in Human Plasma Associates with Proteins Linked to Immunity and Inflammation

Human Plasma Phospholipid Transfer Protein (PLTP) – Structural and Functional Features

Reduced CSF PLTP activity in Alzheimer's disease and other neurologic diseases; PLTP induces ApoE secretion in primary human astrocytes in vitro

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