Caveolin, Sterol Carrier Protein-2, Membrane Cholesterol-Rich Microdomains and Intracellular Cholesterol Trafficking

Schroeder, Friedhelm; Huang, Huan; McIntosh, Avery L.; Atshaves, Barbara P.; Martin, Gregory G.; Kier, Ann B.

doi:10.1007/978-90-481-8622-8_10

Cited by 25 publications

(21 citation statements)

References 190 publications

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“…While kinetic analysis alone does not establish the identity of these two NBD-cholesterol pools, neither pool was attributed to spontaneous diffusion from intracellular sites through the cytosol to the plasma membrane, a much slower process (t 1/2 ϭ 3 h to days) (37). Since the half time of transbilayer cholesterol movement is Ͻ1 min (16), the half times of the rapid (2.4 min) and slowly (26 min) effluxing NBD-cholesterol pools were in the range of those for proteinmediated molecular transfer and vesicular transfer, respectively (6,37 (6,33), while SCP-2 overexpression in rodents inhibits VLDL cholesterol secretion (1,41). SCP-2's role(s) in facilitating retention of HDL-derived cholesterol for biliary cholesterol secretion is supported by rodent studies, where SCP-2 overexpression and SCP-2 antisense treatment increased and decreased, respectively, biliary free cholesterol excretion (1,30,41).…”

Section: Discussionmentioning

confidence: 99%

Effect of sterol carrier protein-2 gene ablation on HDL-mediated cholesterol efflux from cultured primary mouse hepatocytes

Storey¹,

Atshaves²,

McIntosh³

et al. 2010

American Journal of Physiology-Gastrointestinal and Liver Physi

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. Effect of sterol carrier protein-2 gene ablation on HDLmediated cholesterol efflux from cultured primary mouse hepatocytes. Am J Physiol Gastrointest Liver Physiol 299: G244-G254, 2010. First published April 15, 2010 doi:10.1152/ajpgi.00446.2009.-Although HDL-mediated cholesterol transport to the liver is well studied, cholesterol efflux from hepatocytes back to HDL is less well understood. Real-time imaging of efflux of 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino)-23,24-bisnor-5-cholen-3␤-ol (NBD-cholesterol), which is poorly esterified, and [ 3 H]cholesterol, which is extensively esterified, from cultured primary hepatocytes of wild-type and sterol carrier protein-2 (SCP-2) gene-ablated mice showed that 1) NBD-cholesterol efflux was affected by the type of lipoprotein acceptor, i.e., HDL3 over HDL2; 2) NBD-cholesterol efflux was rapid (detected in 1-2 min) and resolved into fast [half time (t1/2) ϭ 2.4 min, 6% of total] and slow (t 1/2 ϭ 26.5 min, 94% of total) pools, consistent with protein-and vesicle-mediated cholesterol transfer, respectively; 3) SCP-2 gene ablation increased efflux of NBD-cholesterol, as well as [3 H]cholesterol, albeit less so due to competition by esterification of [ 3 H]cholesterol, but not NBD-cholesterol; and 4) SCP-2 gene ablation increased initial rate (2.3-fold) and size (9.7-fold) of rapid effluxing sterol, suggesting an increased contribution of molecular cholesterol transfer. In addition, colocalization, double-immunolabeling fluorescence resonance energy transfer, and electron microscopy, as well as cross-linking coimmunoprecipitation, indicated that SCP-2 directly interacted with the HDL receptor, scavenger receptor class B type 1 (SRB1), in hepatocytes. Other membrane proteins in cholesterol efflux [SRB1 and ATP-binding cassettes (ABC) A-1, ABCG-1, ABCG-5, and ABCG-8] and several soluble/vesicle-associated proteins facilitating intracellular cholesterol trafficking (StARDs, NPCs, ORPs) were not upregulated. However, loss of SCP-2 elicited twofold upregulation of liver fatty acid-binding protein (L-FABP), a protein with lower affinity for cholesterol but higher cytosolic concentration than SCP-2. Ablation of SCP-2 and L-FABP decreased HDL-mediated NBD-cholesterol efflux. These results indicate that SCP-2 expression plays a significant role in HDL-mediated cholesterol efflux by regulating the size of rapid vs. slow cholesterol efflux pools and/or eliciting concomitant upregulation of L-FABP in cultured primary hepatocytes. confocal imaging; bile; scavenger receptor B1 EXCESS CHOLESTEROL IS PRIMARILY removed from the body via the liver into bile, and Ͼ95% of excreted cholesterol originates from lipoproteins, primarily HDL (9). HDL removes unesterified (free) cholesterol from tissues, transports free (as well as esterified) cholesterol to the liver, and binds to scavenger receptor class B type 1 (SRB1) at hepatocyte basolateral plasma membranes (9). Hepatic clearance of HDL free cholesterol from blood is rapid [half time (t 1/2 ) ϭ 3 min] (15, 31), consistent with very ra...

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Section: Discussionmentioning

confidence: 99%

Effect of sterol carrier protein-2 gene ablation on HDL-mediated cholesterol efflux from cultured primary mouse hepatocytes

Storey¹,

Atshaves²,

McIntosh³

et al. 2010

American Journal of Physiology-Gastrointestinal and Liver Physi

Self Cite

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“…The overexpression of SCP-2 may finally inhibit HDL-mediated cholesterol efflux. SCP-2 plays a significant role in HDL-mediated cholesterol efflux by regulating the sizes of the rapid vs slow cholesterol efflux pools [75,76] .…”

Section: Scp-2mentioning

confidence: 99%

A novel model of cholesterol efflux from lipid-loaded cells

et al. 2010

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Cholesterol efflux from lipid-loaded cells is a key athero-protective event that counteracts cholesterol uptake. The imbalance between cholesterol efflux and uptake determines the prevention or development of atherosclerosis. Many proteins and factors participate in the cholesterol efflux event. However, there are currently no systematic models of reverse cholesterol transport (RCT) that include most RCT-related factors and events. On the basis of recent research findings from other and our laboratories, we propose a novel model of one center and four systems with coupling transportation and networking regulation. This model represents a common way of cholesterol efflux; however, the systems in the model consist of different proteins/factors in different cells. In this review, we evaluate the novel model in vascular smooth muscle cells (VSMCs) and macrophages, which are the most important original cells of foam cells. This novel model consists of 1) a caveolae transport center, 2) an intracellular trafficking system of the caveolin-1 complex, 3) a transmembrane transport system of the ABC-A1 complex, 4) a transmembrane transport system of the SR-B1 complex, and 5) an extracelluar trafficking system of HDL/Apo-A1. In brief, the caveolin-1 system transports cholesterol from intracellular compartments to caveolae. Subsequently, both ABC-A1 and SR-B1 complex systems transfer cholesterol from caveolae to extracellular HDL/Apo-A1. The four systems are linked by a regulatory network. This model provides a simple and concise way to understand the dynamic process of atherosclerosis.

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“…12) (reviewed in Ref. 49). Although lateral diffusion of cholesterol through the basolateral to the canalicular membrane is also possible (Fig.…”

Section: Discussionmentioning

confidence: 97%

“…12), lateral diffusion through lipid membranes is much too slow (hours) and further slowed by the tight junction, thus not accounting for the observed rapid transcellular transport of HDL-derived free cholesterol (reviewed in Ref. 49). We hypothesize that SCP-2 and L-FABP facilitate the intracellular transport of HDL-derived free cholesterol by binding to SRB1 at the basolateral membrane, binding and transporting cholesterol through the cytosol to SRB1 (and/or ABCG5/ABCG8) at the bile canaliculus to facilitate biliary cosecretion of cholesterol with bile acid (Fig.…”

Section: Discussionmentioning

confidence: 98%

Intracellular cholesterol-binding proteins enhance HDL-mediated cholesterol uptake in cultured primary mouse hepatocytes

Storey¹,

McIntosh²,

Huang³

et al. 2012

American Journal of Physiology-Gastrointestinal and Liver Physi

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A major gap in our knowledge of rapid hepatic HDL cholesterol clearance is the role of key intracellular factors that influence this process. Although the reverse cholesterol transport pathway targets HDL to the liver for net elimination of free cholesterol from the body, molecular details governing cholesterol uptake into hepatocytes are not completely understood. Therefore, the effects of sterol carrier protein (SCP)-2 and liver fatty acid-binding protein (L-FABP), high-affinity cholesterol-binding proteins present in hepatocyte cytosol, on HDL-mediated free cholesterol uptake were examined using gene-targeted mouse models, cultured primary hepatocytes, and 22-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-amino]-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol). While SCP-2 overexpression enhanced NBD-cholesterol uptake, counterintuitively, SCP-2/SCP-x gene ablation also 1) enhanced the rapid molecular phase of free sterol uptake detectable in <1 min and initial rate and maximal uptake of HDL free cholesterol and 2) differentially enhanced free cholesterol uptake mediated by the HDL3, rather than the HDL2, subfraction. The increased HDL free cholesterol uptake was not due to increased expression or distribution of the HDL receptor [scavenger receptor B1 (SRB1)], proteins regulating SRB1 [postsynaptic density protein (PSD-95)/Drosophila disk large tumor suppressor (dlg)/tight junction protein (ZO1) and 17-kDa membrane-associated protein], or other intracellular cholesterol trafficking proteins (steroidogenic acute response protein D, Niemann Pick C, and oxysterol-binding protein-related proteins). However, expression of L-FABP, the single most prevalent hepatic cytosolic protein that binds cholesterol, was upregulated twofold in SCP-2/SCP-x null hepatocytes. Double-immunogold electron microscopy detected L-FABP sufficiently close to SRB1 for direct interaction, similar to SCP-2. These data suggest a role for L-FABP in HDL cholesterol uptake, a finding confirmed with SCP-2/SCP-x/L-FABP null mice and hepatocytes. Taken together, these results suggest that L-FABP, particularly in the absence of SCP-2, plays a significant role in HDL-mediated cholesterol uptake in cultured primary hepatocytes.

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Caveolin, Sterol Carrier Protein-2, Membrane Cholesterol-Rich Microdomains and Intracellular Cholesterol Trafficking

Cited by 25 publications

References 190 publications

Effect of sterol carrier protein-2 gene ablation on HDL-mediated cholesterol efflux from cultured primary mouse hepatocytes

Effect of sterol carrier protein-2 gene ablation on HDL-mediated cholesterol efflux from cultured primary mouse hepatocytes

A novel model of cholesterol efflux from lipid-loaded cells

Intracellular cholesterol-binding proteins enhance HDL-mediated cholesterol uptake in cultured primary mouse hepatocytes

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