Human amnion contains a novel laminin variant, laminin 7, which like laminin 6, covalently associates with laminin 5 to promote stable epithelial-stromal attachment.
Stable attachment of external epithelia to the basement membrane and underlying stroma is mediated by transmembrane proteins such as the integrin alpha6beta4 and bullous pemphigoid antigen 2 within the hemidesmosomes along the basolateral surface of the epithelial cell and their ligands that include a specialized subfamily of laminins. The laminin 5 molecule (previously termed kalinin/nicein/epiligrin) is a member of this epithelial-specific subfamily. Laminin 5 chains are not only considerably truncated within domains III-VI, but are also extensively proteolytically processed in vitro and in vivo. As a result, the domains expected to be required for the association of laminins with other basement membrane components are lacking in the mature laminin 5 molecule. Therefore, the tight binding of laminin 5 to the basement membrane may occur by a unique mechanism. To examine laminin 5 in tissue, we chose human amnion as the source, because of its availability and the similarity of the amniotic epithelial basement membrane with that of skin. We isolated the laminin 5 contained within the basement membrane of human amnion. In addition to monomeric laminin 5, we find that much of the laminin 5 isolated is covalently adducted with laminin 6 (alpha3beta1gamma1) and a novel laminin isotype we have termed laminin 7 (alpha3beta2gamma1). We propose that the association between laminin 5 and laminins 6 and 7 is a mechanism used in amnion to allow stable association of laminin 5 with the basement membrane. The beta2 chain is seen at the human amniotic epithelial-stromal interface and at the dermal-epidermal junction of fetal and adult bovine skin by immunofluorescence, but is not present, or only weakly present, in neonatal human skin.
Champliaud
M F
MF
Cutaneous Biology Research Center, Massachusetts General Hospital, Charlestown 02129, USA.
Lunstrum
G P
GP
Rousselle
P
P
Nishiyama
T
T
Keene
D R
DR
Burgeson
R E
RE
D000328:Adult; D000595:Amino Acid Sequence; D000650:Amnion / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002448:Cell Adhesion / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D003238:Connective Tissue / Q000378:metabolism; D003239:Connective Tissue Cells; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D007797:Laminin / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D000097794:Kalinin
D015815:Cell Adhesion Molecules; D007797:Laminin; D000097794:Kalinin; C098891:laminin 7