Scavenger receptor CL-P1 mediates endocytosis by associating with AP-2μ2

Background: Scavenger receptor CL-P1 (collectin placenta 1) has been found recently as a first membrane-type collectin which is mainly expressed in vascular endothelial cells. CL-P1 can endocytose OxLDL as well as microbes but in general, the endocytosis mechanism of a scavenger receptor is not well elucidated. Methods: We screened a placental cDNA library using a yeast two-hybrid system to detect molecules associated with the cytoplasmic domain of CL-P1 We analyzed the binding and endocytosis of several ligands in CL-P1 transfectants and performed the inhibition study using tyrphostin A23 which is a specific inhibitor of tyrosine kinase, especially in mu 2-dependent endocytosis and the site-directed mutagenesis in the endocytosis YXX Phi motif in CL-P1 cytoplasmic region. Furthermore, the SiRNA study of clathrin, adaptor AP-2 and dynamin-2 during the endocytosis of OxLDL in CL-P1 transfectant cells was carried out. Results: We identified mu 2 subunit of the AP-2 adaptor complex as a molecule associated with the cytoplasmic region of CL-P1. We demonstrated that AP-2 mu 2 was essential for CL-P1 mediated endocytosis of OxLDL in CL-P1 transfectant cells and its endocytosis was also mediated by clathrin, dynamin and adaptin complex molecules. Conclusions: Tyrosine-based YXX Phi sequences play an important role in CL-P1 -mediated OxLDL endocytosis associated with AP-2 mu 2. General Significance: This might be the first finding of the clear endocytosis mechanism in scavenger receptor CL-P1. (C) 2014 Elsevier B.V. All rights reserved.