title: Digestion of C1q collagen-like domain with MMPs-1,-2,-3, and -9 further defines the sequence involved in the stimulation of neutrophil superoxide production.
abstract: C1q, a subunit of the first component (C1) of the classical complement pathway, binds to neutrophils via its collagen-like region (C1q-CLR) stimulating superoxide production. We previously identified a region of C1q-CLR, defined by fragments generated by trypsin and endoLys-C digestion, that was required for triggering this respiratory burst. To further localize that critical site, purified human C1q was digested with pepsin to generate C1q-CLR, and subsequently cleaved with the matrix metalloproteinases, MMP-1, MMP-2, MMP-3, and MMP-9. Digestion of C1q-CLR with any of these MMPs did not alter the circular dichroism spectra, demonstrating that the fragments generated had maintained the secondary structure observed in the native molecule. All fragments retained the ability to trigger superoxide production by neutrophils. Analysis of the amino acid sequences of the purified cleavage products (none of which are identical to the published cleavage site specificities for these enzymes) demonstrated that it is the C-chain, but not the A-chain of C1q, that is critical for stimulating this activity, and thus may be a target for future therapeutic intervention.
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine 92697-3900, USA.
authors.forename: S
authors.initials: S
authors.lastname: Ruiz
authors.forename: A H
authors.initials: AH
authors.lastname: Henschen-Edman
authors.forename: H
authors.initials: H
authors.lastname: Nagase
authors.forename: A J
authors.initials: AJ
authors.lastname: Tenner
mesh_terms: D000595:Amino Acid Sequence; D003094:Collagen / Q000737:chemistry; D017364:Collagenases / Q000378:metabolism*; D015922:Complement C1q / Q000378:metabolism* / Q000494:pharmacology; D018093:Gelatinases / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D020781:Matrix Metalloproteinase 1; D020778:Matrix Metalloproteinase 2; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9; D008666:Metalloendopeptidases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D016897:Respiratory Burst; D013268:Stimulation, Chemical; D013329:Structure-Activity Relationship; D013481:Superoxides / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D013481:Superoxides; D015922:Complement C1q; D003094:Collagen; D017364:Collagenases; D018093:Gelatinases; D008666:Metalloendopeptidases; D019278:Matrix Metalloproteinase 3; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D020781:Matrix Metalloproteinase 1