PLTP secreted by HepG2 cells resembles the high-activity PLTP form in human plasma

Siggins, Sarah; Jauhiainen, Matti; Olkkonen, Vesa M.; Tenhunen, Jukka; Ehnholm, Christian

doi:10.1194/jlr.m300059-jlr200

Cited by 54 publications

(45 citation statements)

References 42 publications

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“…Assuming that our DxSO 4 -CaCl 2 precipitation results in complete separation of HA-and LA-PLTP, the anticipated specific activity recovered in the supernatant would be ‫1.3ف‬ mol/g/h. Our observation that the PLTP present in the supernatant yields a specific activity of 2.6 mol/g/h, similar to that obtained for active PLTP secreted by HepG2 hepatoma cells (40), suggests that the separation we achieved is close to optimal.…”

Section: Discussionsupporting

confidence: 54%

“…We have previously demonstrated by size-exclusion chromatography that LA-PLTP and HA- PLTP are associated with complexes of different size, LA-PLTP eluting at a position corresponding to 520 kDa and HA-PLTP at 160 kDa (28). Furthermore, LA-PLTP is found associated with apoA-I, whereas HA-PLTP is not (29), and active PLTP secreted by HepG2 hepatoma cells (resembling HA-PLTP in plasma) is found associated with apoE (40). As suggested previously (27), it is possible that PLTP adopts a different conformation when associated with particles of different size and surface curvature, which may lead to differential exposure of epitopes.…”

Section: Discussionmentioning

confidence: 58%

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Quantitation of the active and low-active forms of human plasma phospholipid transfer protein by ELISA

Siggins¹,

Kärkkäinen²,

Tenhunen

et al. 2004

Journal of Lipid Research

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Human plasma contains two forms of phospholipid transfer protein (PLTP), one catalytically active [highactivity PLTP (HA-PLTP)] and the other a low-activity (LA-PLTP) form. We present here a PLTP ELISA that allows not only for accurate measurement of PLTP concentration in plasma but also of the distribution of both LA-and HA-PLTP. To achieve similar immunoreactivity of the two PLTP forms, a denaturing sample pretreatment with 0.5% SDS was required. Distribution of LA-and HA-PLTP in plasma was assessed using size-exclusion chromatography, Heparin-Sepharose chromatography, anti-PLTP immunoaffinity chromatography, and dextran sulfate-CaCl 2 precipitation. All four methods demonstrated that ‫ف‬ 60% of plasma PLTP represents LA-PLTP and 40% represents HA-PLTP. According to the modified ELISA, the total serum PLTP concentration in a random Finnish population sample (n ‫؍‬ 80) was 5.81 ؎ 1.33 mg/l (mean ؎ SD) (range, 2.78-10.06 mg/l) and the mean activity was 5.84 ؎ 1.39 mol/ml/h (range, 3.21-11.15 mol/ml/h).To quantitate both forms of PLTP in sera from this sample, we combined dextran sulfate-CaCl 2 precipitation with the modified PLTP ELISA. Other in vitro functions demonstrated are proteolysis of apolipoprotein A-I (apoA-I) (3), HDL interconversion (4, 5), and the stimulation of LCAT and cholesteryl ester transfer protein activity (6).Studies in genetically manipulated mice with altered PLTP expression have advanced our understanding of the metabolic functions of PLTP (7-16). PLTP has three major functions in HDL metabolism: it transfers surface remnants from VLDL to HDL during lipolysis (7), it increases the catabolism of HDL and the generation of pre-␤ -HDL, and it stimulates cellular cholesterol/PL efflux (9-12). PLTP has also been shown to play a role in the secretion of apoB-containing lipoproteins (15,17,18).Although the in vitro role of PLTP in gene-targeted animal models has been studied intensively, the physiological role of PLTP in human lipid metabolism is far from resolved. To obtain information about the role of PLTP in human metabolism, one approach has been to assess PLTP activity under different physiological conditions (19)(20)(21)(22). Moreover, to gain a more complete understanding of the metabolic role of PLTP, its mass in plasma should also be recorded (23-26). To date, three different methods to assay plasma PLTP mass have been reported, with conflicting results (23-25). A possible reason for the discrepancies may be differences in the immunoreactivity of the antibodies used, as reported by Murdoch et al. (27), and the presence of two forms of PLTP in the circulation (28, 29). The two forms, one catalytically active [high-activity PLTP (HA-PLTP)] and the other low-activity (LA-PLTP), are associated with distinct macromolecular complexes of different size and eventually display different immunochemical reactivities. The observation that PLTP mass and activity in human plasma do not correlate (24, 25) further suggests differences in the reactivity of antibodies to HAAbbreviations: HA-PLT...

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Section: Discussionsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 58%

Quantitation of the active and low-active forms of human plasma phospholipid transfer protein by ELISA

Siggins¹,

Kärkkäinen²,

Tenhunen

et al. 2004

Journal of Lipid Research

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“…The active form of PLTP copurifies with apoE, whereas the inactive form is associated with apoAI (32). In addition, active PLTP secreted from HepG2 cells coelutes with apoE but not with apoAI (46). Furthermore, apoE but not apoAI is able to convert inactive PLTP into the active form (34).…”

Section: Discussionmentioning

confidence: 93%

Plasma Phospholipid Transfer Protein Activity Is Decreased in Type 2 Diabetes During Treatment With Atorvastatin

Dallinga‐Thie

Tol²,

Hashimoto³

et al. 2006

Diabetes

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Plasma phospholipid transfer protein (PLTP) plays an important role in lipoprotein metabolism. PLTP activity is elevated in patients with diabetes, a condition with strongly elevated risk for coronary heart disease. The aim of this study was to test the hypothesis that statins reduce PLTP activity and to examine the potential role of apolipoprotein E (apoE). PLTP activity and apoE were measured in patients with type 2 diabetes from the DALI (Diabetes Atorvastatin Lipid Intervention) Study, a 30-week randomized double-blind placebo-controlled trial with atorvastatin (10 and 80 mg daily). At baseline, PLTP activity was positively correlated with waist circumference, HbA 1c , glucose, and apoE (all P < 0.05). Atorvastatin treatment resulted in decreased PLTP activity (10 mg atorvastatin: ؊8.3%, P < 0.05; 80 mg atorvastatin: ؊12.1%, P < 0.002). Plasma apoE decreased by 28 and 36%, respectively (P < 0.001). The decrease in apoE was strongly related to the decrease in PLTP activity (r ‫؍‬ 0.565, P < 0.001). The change in apoE remained the sole determinant of the change in PLTP activity in a multivariate model. The activity of PLTP in type 2 diabetes is decreased by atorvastatin. The association between the decrease in PLTP activity and apoE during statin treatment supports the hypothesis that apoE may prevent PLTP inactivation.

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“…The heparin-bound apoE-containing HDL was detached via elution with 5 mM Tris-HCl, 100 mM NaCl, pH 7.4. ApoE was analyzed in isolated HDL pools by ELISA (21).…”

Section: Methodsmentioning

confidence: 99%

Complement Factor H Binds to Human Serum Apolipoprotein E and Mediates Complement Regulation on High Density Lipoprotein Particles

Haapasalo

Kessel

Nissilä

et al. 2015

Journal of Biological Chemistry

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Background: Factor H is the main complement alternative pathway regulator in plasma. Results: Factor H binds to apoE leading to reduced complement activity against HDL particles. Conclusion: Interaction of factor H with HDL particles is involved in complement regulation in plasma. Significance: Complement regulation on HDL particles by factor H could be involved in disease processes caused by alternative pathway dysregulation.

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PLTP secreted by HepG2 cells resembles the high-activity PLTP form in human plasma

Cited by 54 publications

References 42 publications

Quantitation of the active and low-active forms of human plasma phospholipid transfer protein by ELISA

Quantitation of the active and low-active forms of human plasma phospholipid transfer protein by ELISA

Plasma Phospholipid Transfer Protein Activity Is Decreased in Type 2 Diabetes During Treatment With Atorvastatin

Complement Factor H Binds to Human Serum Apolipoprotein E and Mediates Complement Regulation on High Density Lipoprotein Particles

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