Activation of ERK and NF-κB during HARE-Mediated Heparin Uptake Require Only One of the Four Endocytic Motifs.
Fifteen different ligands, including heparin (Hep), are cleared from lymph and blood by the Hyaluronan (HA) Receptor for Endocytosis (HARE; derived from Stabilin-2 by proteolysis), which contains four endocytic motifs (M1-M4). Endocytosis of HARE•Hep complexes is targeted to coated pits by M1, M2, and M3 (Pandey et al, Int. J. Cell Biol. 2015, article ID 524707), which activates ERK1/2 and NF-κB (Pandey et al J. Biol. Chem. 288, 14068-79, 2013). Here, we used a NF-κB promoter-driven luciferase gene assay and cell lines expressing different HARE cytoplasmic domain mutants to identify motifs needed for Hep-mediated signaling. Deletion of M1, M2 or M4 singly had no effect on Hep-mediated ERK1/2 activation, whereas signaling (but not uptake) was eliminated in HARE(ΔM3) cells lacking NPLY2519. ERK1/2 signaling in cells expressing WT HARE(Y2519A) or HARE(Y2519A) lacking M1, M2 and M4 (containing M3-only) was decreased by 75% or eliminated, respectively. Deletion of M3 (but not M1, M2 or M4) also inhibited the formation of HARE•Hep•ERK1/2 complexes by 67%. NF-κB activation by HARE-mediated uptake of Hep, HA, dermatan sulfate or acetylated LDL was unaffected in single-motif deletion mutants lacking M1, M2 or M4. In contrast, cells expressing HARE(ΔM3) showed loss of HARE-mediated NF-κB activation during uptake of each of these four ligands. NF-κB activation by the four signaling ligands was also eliminated in HARE(Y2519A) or HARE(M3-only;Y2519A) cells. We conclude that the HARE NPLY2519 motif is necessary for both ERK1/2 and NF-κB signaling and that Tyr2519 is critical for these functions.
Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, United States of America.
Madhu S
MS
Pandey
Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, United States of America.
Colton M
CM
Miller
Department of Biochemistry, University of Nebraska, Lincoln, NE 68588, United States of America.
Edward N
EN
Harris
Department of Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, United States of America.
Paul H
PH
Weigel
D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D015153:Blotting, Western; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000378:metabolism*; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D004705:Endocytosis / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D057809:HEK293 Cells; D006493:Heparin / Q000493:pharmacokinetics* / Q000494:pharmacology; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009154:Mutation; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D015398:Signal Transduction / Q000235:genetics; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
D015816:Cell Adhesion Molecules, Neuronal; D016328:NF-kappa B; C449927:STAB2 protein, human; D014443:Tyrosine; D006493:Heparin; D008156:Luciferases; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3