Complex determinants in specific members of the mannose receptor family govern collagen endocytosis.
Members of the well-conserved mannose receptor (MR) protein family have been functionally implicated in diverse biological and pathological processes. Importantly, a proposed common function is the internalization of collagen for intracellular degradation occurring during bone development, cancer invasion, and fibrosis protection. This functional relationship is suggested by a common endocytic capability and a candidate collagen-binding domain. Here we conducted a comparative investigation of each member's ability to facilitate intracellular collagen degradation. As expected, the family members uPARAP/Endo180 and MR bound collagens in a purified system and internalized collagens for degradation in cellular settings. In contrast, the remaining family members, PLA2R and DEC-205, showed no collagen binding activity and were unable to mediate collagen internalization. To pinpoint the structural elements discriminating collagen from non-collagen receptors, we constructed a series of receptor chimeras and loss- and gain-of-function mutants. Using this approach we identified a critical collagen binding loop in the suggested collagen binding region (an FN-II domain) in uPARAP/Endo180 and MR, which was different in PLA2R or DEC-205. However, we also found that an active FN-II domain was not a sufficient determinant to allow collagen internalization through these receptors. Nevertheless, this ability could be acquired by the transfer of a larger segment of uPARAP/Endo180 (the Cys-rich domain, the FN-II domain and two CTLDs) to DEC-205. These data underscore the importance of the FN-II domain in uPARAP/Endo180 and MR-mediated collagen internalization but at the same time uncover a critical interplay with flanking domains.
From the Finsen Laboratory, Rigshospitalet/Biotech Research and Innovation Center (BRIC), DK-2200 Copenhagen, Denmark and.
Henrik J
HJ
Jürgensen
Kristina
K
Johansson
Daniel H
DH
Madsen
Astrid
A
Porse
Maria C
MC
Melander
Kristine R
KR
Sørensen
Christoffer
C
Nielsen
Thomas H
TH
Bugge
Niels
N
Behrendt
Lars H
LH
Engelholm
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D003094:Collagen / Q000737:chemistry*; D004330:Drosophila; D004705:Endocytosis; D005347:Fibroblasts / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D007313:Insecta; D037181:Lectins, C-Type / Q000737:chemistry*; D008024:Ligands; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000737:chemistry*; D008562:Membrane Glycoproteins / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry*; D011975:Receptors, Mitogen / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
C408294:Endo180; D037181:Lectins, C-Type; D008024:Ligands; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D011975:Receptors, Mitogen; D003094:Collagen
Cancer Invasion; Collagen; Endocytosis; Extracellular Matrix; Intracellular Collagen Degradation; Mannose Receptor; Mannose Receptor Family; Protein Chimeras; Receptor Structure-Function; uPARAP/Endo180