Human Serum Paraoxonase/Arylesterase’s Retained Hydrophobic
            <i>N</i>
            -Terminal Leader Sequence Associates With HDLs by Binding Phospholipids

Sorenson, Robert C.; Bisgaier, Charles L.; Aviram, Michael; Hsu, C.; Billecke, Scott S.; Du, Bert N. La

doi:10.1161/01.atv.19.9.2214

Cited by 296 publications

(257 citation statements)

References 56 publications

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“…Based on preceding studies we proposed that HDL acquires PON1 by desorption from a plasma membrane location in cells synthesizing the enzyme [10], as also suggested by others [23]. Thus we examined whether PON1 transferred into the cell membrane could relocate to HDL.…”

Section: Pon1 Can Shuttle Between the Cell Membrane And Hdlmentioning

confidence: 77%

HDL-associated paraoxonase-1 can redistribute to cell membranes and influence sensitivity to oxidative stress

Deakin

Bioletto

Bochaton‐Piallat

et al. 2011

Free Radical Biology and Medicine

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a b s t r a c t a r t i c l e i n f oParaoxonase-1 (PON1) is a high-density lipoprotein (HDL)-associated serum enzyme thought to make a major contribution to the antioxidant capacity of the lipoprotein. In previous studies, we proposed that HDL promoted PON1 secretion by transfer of the enzyme from its plasma membrane location to HDL transiently anchored to the hepatocyte. This study examined whether PON1 can be transferred into cell membranes and retain its enzymatic activities and functions. Using Chinese hamster ovary and human endothelial cells, we found that recombinant PON1 as well as PON1 associated with purified human HDL was freely exchanged between the external medium and the cell membranes. Transferred PON1 was located in the external face of the plasma membrane of the cells in an enzymatically active form. The transfer of PON1 led to a gain of function by the target cells, as revealed by significantly reduced susceptibility to oxidative stress and significantly increased ability to neutralize the bacterial virulence agent 3-oxo-C 12 -homoserine lactone. The data demonstrate that PON1 is not a fixed component of HDL and suggest that the enzyme could also exert its protective functions outside the lipoprotein environment. The observations may be of relevance to tissues exposed to oxidative stress and/or bacterial infection.

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Section: Pon1 Can Shuttle Between the Cell Membrane And Hdlmentioning

confidence: 77%

HDL-associated paraoxonase-1 can redistribute to cell membranes and influence sensitivity to oxidative stress

Deakin

Bioletto

Bochaton‐Piallat

et al. 2011

Free Radical Biology and Medicine

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“…Moreover, deletion of PON's hydrophobic N-terminal domain was found to abrogate the association of PON with reconstituted HDL, leading to the conclusion that this region serves to anchor PON to HDL particles through, primarily, protein-phospholipid interactions (16). This interpretation, however, does not sufficiently address the exclusive affinity of PON with specific subpopulations of apoA-I containing HDL found in human plasma (15).…”

Section: Discussionmentioning

confidence: 90%

Cysteine Substitutions in Apolipoprotein A-I Primary Structure Modulate Paraoxonase Activity

et al. 2001

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Paraoxonase (PON) is transported primarily on apolipoprotein A-I (apoA-I) -containing highdensity lipoprotein (HDL) and is thought to protect against early atherogenic events including low-density lipoprotein (LDL) oxidation and monocyte migration. It has been proposed that apoA-I may be necessary for PON's association with plasma HDL. On the basis of this, we examined the effect of apoA-I on PON's enzymatic activity and its ability to associate with HDL. Additionally, we examined whether changes in apoA-I primary structure (cysteine substitution mutations) could modulate these effects. Chinese hamster ovary cells stably transfected with human PON1A cDNA were incubated in the presence and absence of recombinant wild-type apoA-I (apoA-I WT ) and specific Cys substitution mutations. Extracellular accumulation of PON activity in the presence of apoA-I WT was 0.095 ( 0.013 unit/mg of cell protein (n ) 7) compared to 0.034 ( 0.010 unit/mg of cell protein in the absence of apoA-I (n ) 7), a 2.79-fold increase in activity when apoA-I was incubated with the cells. Lipid-free apoA-I did not increase PON activity, while preformed nascent HDL increased PON activity only 30%, suggesting that maximal PON activity is lipid-dependent and requires coassembly of PON and apoA-I on nascent HDL. The cysteine mutations R10C, R27C, and R61C significantly increased (p < 0.01) PON activity 32.6% ( 14.7%, 31.6% ( 18.9%, and 27.4% ( 20%, respectively, over that of wild type (WT). No changes in PON activity were observed with apoA-I cysteine substitution mutations in the C-terminal portion of the protein.The data suggest that, for optimal PON activity, coassembly of the enzyme onto nascent HDL is required and that the N-terminal region of apoA-I may be important in the assembly process.

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“…The observations that POPC vesicles and rHDLAII can promote release are interesting. They may offer one explanation for the presence of PON1 in apoA-I knockout models (30) and in human HDL deficiency syndromes (20). This is of clinical relevance as it suggests that HDL deficiency does not necessarily mean absence of an anti-atherogenic mechanism thought to depend on HDL.…”

Section: Discussionmentioning

confidence: 95%

Enzymatically Active Paraoxonase-1 Is Located at the External Membrane of Producing Cells and Released by a High Affinity, Saturable, Desorption Mechanism

Deakin

Leviev

Gomaraschi

et al. 2002

Journal of Biological Chemistry

219

186

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Paraoxonase-1 (PON1) is a high density lipoprotein (HDL)-associated serum enzyme that protects low density lipoproteins from oxidative modifications. There is a relative lack of information on mechanisms implicated in PON1 release from cells. The present study focused on a model derived from stable transfection of CHO cells, to avoid co-secretion of apolipoprotein (apo) A-I and lipids, which could lead to formation of HDL-like complexes. Our results indicate that, in the absence of an appropriate acceptor, little PON1 is released. The results designate HDL as the predominant, physiological acceptor, whose efficiency is influenced by size and composition. Neither lipid-poor apoA-I or apoA-II nor low density lipoproteins could substitute for HDL. Protein-free phospholipid complexes promoted PON1 release. However, the presence of both apolipoprotein and phospholipid were necessary to promote release and stabilize the enzyme. Immunofluorescence studies demonstrated that PON1 was inserted into the external membrane of CHO cells, where it was enzymatically active. Accumulation of PON1 in the cell membrane was not influenced by the ability of the cell to co-secrete of apoA-I. Release appeared to involve desorption by HDL; human and reconstituted HDL promoted PON1 release in a saturable, high affinity manner (apparent affinity 1.59 ؎ 0.3 g of HDL protein/ml). Studies with PON1-transfected hepatocytes (HuH-7) revealed comparable structural features with the peptide located in a punctate pattern at the external membrane and enzymatically active. We hypothesize that release of PON1 involves a docking process whereby HDL transiently associate with the cell membrane and remove the peptide from the external membrane. The secretory process may be of importance for assuring the correct lipoprotein destination of PON1 and thus its functional efficiency. Paraoxonase-1 (PON1)1 is a high density lipoprotein (HDL)-associated serum enzyme that protects low density lipoproteins (LDL) from oxidative modifications. In vitro studies have demonstrated the capacity of PON1 to prevent LDL (and HDL) oxidation by a variety of pro-oxidant factors, including cellinduced LDL oxidation (1, 2). Complementary studies have shown that the anti-oxidant activity of PON1 prevents LDL from acquiring a number of pathological characteristics associated with the atherosclerotic process, notably monocyte mobilization and gene activation (3). The PON1 knockout mouse model confirmed that absence of serum PON1 activity increases the level of lipoprotein oxidation, renders LDL more susceptible to oxidation, decreases the anti-oxidant capacity of HDL and leads to more extensive atheroma formation (4, 5). In man, we first demonstrated that PON1 was an independent, genetic risk factor for coronary disease (6, 7). This has been confirmed independently (8 -11), although not consistently (12,13). In subsequent studies we have shown that PON1 promoter polymorphisms, which affect promoter activity and serum PON1 concentrations (14), are also independent risk factors for...

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Human Serum Paraoxonase/Arylesterase’s Retained Hydrophobic N -Terminal Leader Sequence Associates With HDLs by Binding Phospholipids

Cited by 296 publications

References 56 publications

HDL-associated paraoxonase-1 can redistribute to cell membranes and influence sensitivity to oxidative stress

HDL-associated paraoxonase-1 can redistribute to cell membranes and influence sensitivity to oxidative stress

Cysteine Substitutions in Apolipoprotein A-I Primary Structure Modulate Paraoxonase Activity

Enzymatically Active Paraoxonase-1 Is Located at the External Membrane of Producing Cells and Released by a High Affinity, Saturable, Desorption Mechanism

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