| First Author | Dib K | Year | 2017 |
| Journal | J Biol Chem | Volume | 292 |
| Issue | 16 | Pages | 6703-6714 |
| PubMed ID | 28235798 | Mgi Jnum | J:242510 |
| Mgi Id | MGI:5905512 | Doi | 10.1074/jbc.M116.768598 |
| Citation | Dib K, et al. (2017) The cytoplasmic tail of L-selectin interacts with the adaptor-protein complex AP-1 subunit mu1A via a novel basic binding motif. J Biol Chem 292(16):6703-6714 |
| abstractText | L-selectin regulates leukocyte adhesion and rolling along the endothelium. Proteins binding to the cytoplasmic tail of L-selectin regulate L-selectin functions. We used L-selectin cytoplasmic tail peptide pulldown assays combined with high sensitivity liquid chromatography/mass spectrometry to identify novel L-selectin tail-binding proteins. Incubation of the L-selectin tail with cell extracts from phorbol 12-myristate 13-acetate-stimulated Raw 264.7 macrophages resulted in the binding of mu1A of the clathrin-coated vesicle AP-1 complex. Furthermore, full-length GST-mu1A and the GST-mu1A C-terminal domain, but not the GST-mu1A N-terminal domain, bind to L-selectin tail peptide, and the intracellular pool of L-selectin colocalizes with AP-1 at the trans-Golgi network. We identified a novel basic protein motif consisting of a cluster of three dibasic residues (356RR357, 359KK360, and 362KK363) in the membrane-proximal domain of the L-selectin tail as well as a doublet of aspartic acid residues (369DD370) in the membrane-distal end of the L-selectin tail involved in mu1A binding. Stimulation of Raw 264.7 macrophages with PMA augmented the amount of mu1A associated with anti-L-selectin immunoprecipitates. However, full-length GST-mu1A did not bind to the phospho-L-selectin tail or phospho-mimetic S364D L-selectin tail. Accordingly, we propose that phosphorylation of mu1A is required for interaction with the L-selectin tail and that L-selectin tail phosphorylation may regulate this interaction in vivo Molecular docking of the L-selectin tail to mu1A was used to identify the mu1A surface domain binding the L-selectin tail and to explain how phosphorylation of the L-selectin tail abrogates mu1A interaction. Our findings indicate that L-selectin is transported constitutively by the AP-1 complex, leading to the formation of a trans-Golgi network reserve pool and that phosphorylation of the L-selectin tail blocks AP-1-dependent retrograde transport of L-selectin. |
