title: Identification of small PDZK1-associated protein, DD96/MAP17, as a regulator of PDZK1 and plasma high density lipoprotein levels.
abstract: Scavenger receptor class B, type I (SR-BI) is the high density lipoprotein (HDL) receptor essential for hepatic uptake of HDL cholesterol. SR-BI was shown to impact plasma HDL levels and be anti-atherogenic. Thus, the ability to regulate hepatic SR-BI may allow for the modulation of plasma HDL cholesterol and progression of atherosclerosis. However, regulation of SR-BI in liver is not well understood. Recently, the PDZ domain containing protein PDZK1 was shown to interact with SR-BI and may serve an essential role in SR-BI cell surface expression. Here we identify an in vivo PDZK1-interacting protein that we named small PDZK1-associated protein (SPAP; also known as DD96/MAP17). Unexpectedly, we found that hepatic overexpression of SPAP in mice resulted in liver deficiency of PDZK1. The absence of PDZK1 in SPAP transgenic mice resulted in a deficiency of SR-BI in liver and markedly increased plasma HDL. Metabolic labeling experiments showed that the proteasome plays a role in the turnover of newly synthesized PDZK1, but that SPAP overexpression in liver increased PDZK1 turnover in an alternate, proteasome-independent pathway. Thus, SPAP may be an endogenous regulator of cellular PDZK1 levels by regulating PDZK1 turnover.
authors.affiliation: Department of Medicine, Division of Molecular Medicine, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA. dls51@columbia.edu
authors.forename: David L
authors.initials: DL
authors.lastname: Silver
authors.forename: Nan
authors.initials: N
authors.lastname: Wang
authors.forename: Silke
authors.initials: S
authors.lastname: Vogel
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D018955:CD36 Antigens / Q000235:genetics / Q000502:physiology; D008076:Cholesterol, HDL / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D003546:Cysteine Endopeptidases; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors; D009363:Neoplasm Proteins; D046988:Proteasome Endopeptidase Complex; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D014162:Transfection
chemical_list: D018955:CD36 Antigens; D008076:Cholesterol, HDL; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; C509768:PDZK1IP1 protein, human; C509767:Pdzk1ip1 protein, mouse; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C495124:SCARB1 protein, human; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; C067713:lactacystin; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine