Bone morphogenetic protein 1 is an extracellular processing enzyme of the laminin 5 gamma 2 chain.
Epithelial cells maintained in culture medium containing low calcium proteolytically process laminin 5 (alpha3beta3gamma2) within the alpha3 and gamma2 chains (). Experiments were designed to identify the enzyme(s) responsible for the laminin 5 processing and the sites of proteolytic cleavage. To characterize the nature of laminin 5 processing, we determined the N-terminal amino acid sequences of the proteolytic fragments produced by the processing events. The results indicate that the first alpha3 chain cleavage (200-l65 kDa alpha3) occurs within subdomain G4 of the G domain. The second cleavage (l65-l45 kDa alpha3) occurs within the lIla domain, 11 residues N-terminal to the start of domain II. The gamma chain is cleaved within the second epidermal growth factor-like repeat of domain Ill. The sequence cleaved within the gamma2 chain matches the consensus sequence for the cleavage of type I, II, and III procollagens by bone morphogenetic protein-1 (BMP-1), also known as type I procollagen C-proteinase (). Recombinant BMP-1 cleaves gamma2 in vitro, both within intact laminin 5 and at the predicted site of a recombinant gamma2 short arm. alpha3 is also cleaved by BMP-1 in vitro, but the cleavage site is yet to be determined. These results show the laminin alpha3 and gamma2 chains to be substrates for BMP-1 in vitro. We speculate that gamma2 cleavage is required for formation of the laminin 5-6 complex and that this complex is directly involved in assembly of the interhemidesmosomal basement membrane. This further suggests that BMP-1 activity facilitates basement membrane assembly, but not hemidesmosome assembly, in the laminin 5-rich dermal-epidermal junction basement membrane in vivo.
Amano
S
S
MGH/Harvard Cutaneous Biology Research Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Scott
I C
IC
Takahara
K
K
Koch
M
M
Champliaud
M F
MF
Gerecke
D R
DR
Keene
D R
DR
Hudson
D L
DL
Nishiyama
T
T
Lee
S
S
Greenspan
D S
DS
Burgeson
R E
RE
D000818:Animals; D001483:Base Sequence; D055395:Bone Morphogenetic Protein 1; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D017931:DNA Primers; D006801:Humans; D006868:Hydrolysis; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D007797:Laminin / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism
D019485:Bone Morphogenetic Proteins; D017931:DNA Primers; D007797:Laminin; D011994:Recombinant Proteins; D008666:Metalloendopeptidases; C525705:BMP1 protein, human; D055395:Bone Morphogenetic Protein 1