A novel mechanism for controlling the activity of alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein. Multiple regulatory sites for 39-kDa receptor-associated protein.

Williams, Suzanne E.; Ashcom, James; Argraves, W. Scott; Strickland, Dudley K.

doi:10.1016/s0021-9258(19)50384-2

Cited by 327 publications

(51 citation statements)

References 38 publications

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“…Heparinase was purchased from Sigma Chemical Company (St. Louis, MO). Recombinant human receptorassociated protein (RAP) was produced as a fusion protein and purified as described previously (27). The carboxyl-terminal fragment of human LPL (amino acid residues 313-448) was produced in E. coli as a fusion protein with glutathione S -transferase (GST) as described previously (28) and designated as GST-LPLC.…”

Section: Methodsmentioning

confidence: 99%

Hepatic triglyceride lipase promotes low density lipoprotein receptor-mediated catabolism of very low density lipoproteins in vitro

Medh

Bowen

Fry

et al. 1999

Journal of Lipid Research

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We demonstrate here that hepatic triglyceride lipase (HTGL) enhances VLDL degradation in cultured cells by a LDL receptor-mediated mechanism. VLDL binding at 4 ؇ C and degradation at 37 ؇ C by normal fibroblasts was stimulated by HTGL in a dose-dependent manner. A maximum increase of up to 7-fold was seen at 10 g/ml HTGL. Both VLDL binding and degradation were significantly increased (4-fold) when LDL receptors were up-regulated by treatment with lovastatin. HTGL also stimulated VLDL degradation by LDL receptor-deficient FH fibroblasts but the level of maximal degradation was 40-fold lower than in lovastatintreated normal fibroblasts. A prominent role for LDL receptors was confirmed by demonstration of similar HTGLpromoted VLDL degradation by normal and LRP-deficient murine embryonic fibroblasts. HTGL enhanced binding and internalization of apoprotein-free triglyceride emulsions, however, this was LDL receptor-independent. HTGLstimulated binding and internalization of apoprotein-free emulsions was totally abolished by heparinase indicating that it was mediated by HSPG. In a cell-free assay HTGL competitively inhibited the binding of VLDL to immobilized LDL receptors at 4 ؇ C suggesting that it may directly bind to LDL receptors but may not bind VLDL particles at the same time. We conclude that the ability of HTGL to enhance VLDL degradation is due to its ability to concentrate lipoprotein particles on HSPG sites on the cell surface leading to LDL receptor-mediated endocytosis and degradation. -Medh, J.

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Section: Methodsmentioning

confidence: 99%

Hepatic triglyceride lipase promotes low density lipoprotein receptor-mediated catabolism of very low density lipoproteins in vitro

Medh

Bowen

Fry

et al. 1999

Journal of Lipid Research

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“…The appropriate delivery of members of the LDL receptor family to the cell surface requires the 39 kDa RAP. RAP is an ER resident protein (Strickland et al, 1991) that binds tightly to members of the LDL receptor family and prevents them from associating with other ligands (Herz et al, 1991;Williams et al, 1992). RAP associates with LRP early in the secretory pathway, reducing its ligand binding capacity, and then dissociates from LRP at the lower pH encountered in the Golgi (Bu et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

RAP Uses a Histidine Switch to Regulate Its Interaction with LRP in the ER and Golgi

et al. 2006

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The receptor associated protein (RAP) is an antagonist and molecular chaperone that binds tightly to low-density lipoprotein receptor family members in the endoplasmic reticulum (ER). After escorting these receptors to the Golgi, RAP dissociates from the receptors. The molecular mechanism of the dissociation has been unknown until now. The solution structure of RAP-D3 domain presented here reveals a striking increase in positively charged residues on the surface of this RAP domain due to protonation of solvent-exposed histidine sidechains as the pH is reduced from a near neutral pH of the ER to the acidic pH of the Golgi. Structure-based mutagenesis studies in vitro and in cells confirm that the protonation of histidine residues as a consequence of the pH changes modulate the binding/release of RAP from LRP. This histidine switch may serve as a general mechanism for regulating cell trafficking events.

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“…RAP was described as a molecular chaperone for LRP1 and antagonist for its interactions with ligands ( 16 , 17 , 18 ). This indicates that RAP may also serve the chaperone function for other LDLR family receptors, which is supported by several studies ( 19 , 20 , 21 , 22 ).…”

mentioning

confidence: 99%

Molecular chaperone RAP interacts with LRP1 in a dynamic bivalent mode and enhances folding of ligand-binding regions of other LDLR family receptors

Marakasova

Olivares

Karnaukhova

et al. 2021

Journal of Biological Chemistry

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The low-density lipoprotein receptor (LDLR) family of receptors are cell-surface receptors that internalize numerous ligands and play crucial role in various processes, such as lipoprotein metabolism, hemostasis, fetal development, etc. Previously, receptor-associated protein (RAP) was described as a molecular chaperone for LDLR-related protein 1 (LRP1), a prominent member of the LDLR family. We aimed to verify this role of RAP for LRP1 and two other LDLR family receptors, LDLR and vLDLR, and to investigate the mechanisms of respective interactions using a cell culture model system, purified system, and in silico modelling. Upon coexpression of RAP with clusters of the ligand-binding complement repeats (CRs) of the receptors in secreted form in insect cells culture, the isolated proteins had increased yield, enhanced folding, and improved binding properties compared with proteins expressed without RAP, as determined by circular dichroism and surface plasmon resonance. Within LRP1 CR-clusters II and IV, we identified multiple sites comprised of adjacent CR doublets, which provide alternative bivalent binding combinations with specific pairs of lysines on RAP. Mutational analysis of these lysines within each of isolated RAP D1/D2 and D3 domains having high affinity to LRP1 and of conserved tryptophans on selected CR-doublets of LRP1, as well as in silico docking of a model LRP1 CR-triplet with RAP, indicated a universal role for these residues in interaction of RAP and LRP1. Consequently, we propose a new model of RAP interaction with LDLR family receptors based on switching of the bivalent contacts between molecules over time in a dynamic mode.

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A novel mechanism for controlling the activity of alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein. Multiple regulatory sites for 39-kDa receptor-associated protein.

Cited by 327 publications

References 38 publications

Hepatic triglyceride lipase promotes low density lipoprotein receptor-mediated catabolism of very low density lipoproteins in vitro

Hepatic triglyceride lipase promotes low density lipoprotein receptor-mediated catabolism of very low density lipoproteins in vitro

RAP Uses a Histidine Switch to Regulate Its Interaction with LRP in the ER and Golgi

Molecular chaperone RAP interacts with LRP1 in a dynamic bivalent mode and enhances folding of ligand-binding regions of other LDLR family receptors

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