| First Author | Kocher O | Year | 2011 |
| Journal | J Biol Chem | Volume | 286 |
| Issue | 28 | Pages | 25171-86 |
| PubMed ID | 21602281 | Mgi Jnum | J:175397 |
| Mgi Id | MGI:5285481 | Doi | 10.1074/jbc.M111.242362 |
| Citation | Kocher O, et al. (2011) Identification of the PDZ3 domain of the adaptor protein PDZK1 as a second, physiologically functional binding site for the C terminus of the high density lipoprotein receptor scavenger receptor class B type I. J Biol Chem 286(28):25171-86 |
| abstractText | The normal expression, cell surface localization, and function of the murine high density lipoprotein receptor scavenger receptor class B type I (SR-BI) in hepatocytes in vivo, and thus normal lipoprotein metabolism, depend on its four PDZ domain (PDZ1-PDZ4) containing cytoplasmic adaptor protein PDZK1. Previous studies showed that the C terminus of SR-BI ('target peptide') binds directly to PDZ1 and influences hepatic SR-BI protein expression. Unexpectedly an inactivating mutation in PDZ1 (Tyr(20) --> Ala) only partially, rather than completely, suppresses the ability of PDZK1 to control hepatic SR-BI. We used isothermal titration calorimetry to show that PDZ3, but not PDZ2 or PDZ4, can also bind the target peptide (K(d) = 37.0 mum), albeit with approximately 10-fold lower affinity than PDZ1. This binding is abrogated by a Tyr(253) --> Ala substitution. Comparison of the 1.5-A resolution crystal structure of PDZ3 with its bound target peptide ((505)QEAKL(509)) to that of peptide-bound PDZ1 indicated fewer target peptide stabilizing atomic interactions (hydrogen bonds and hydrophobic interactions) in PDZ3. A double (Tyr(20) --> Ala (PDZ1) + Tyr(253) --> Ala (PDZ3)) substitution abrogated all target peptide binding to PDZK1. In vivo hepatic expression of a singly substituted (Tyr(253) --> Ala (PDZ3)) PDZK1 transgene (Tg) was able to correct all of the SR-BI-related defects in PDZK1 knock-out mice, whereas the doubly substituted [Tyr(20) --> Ala (PDZ1) + Tyr(253) --> Ala (PDZ3)]Tg was unable to correct these defects. Thus, we conclude that PDZK1-mediated control of hepatic SR-BI requires direct binding of the SR-BI C terminus to either the PDZ1 or PDZ3 domains, and that binding to both domains simultaneously is not required for PDZK1 control of hepatic SR-BI. |
