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lamina propria 438 laminin receptor
lamina propria
The thin connective tissue layer that supports the epithelium
of the gastrointestinal tract. The epithelium and lamina propria
form the mucous membrane. The lamina propria may
be the site of immunologic reactivity in the gastrointestinal
tract, representing an area where lymphocytes, plasma cells,
and mast cells congregate.
laminin
A relatively large (820-kDa) basement membrane glycoprotein
composed of three polypeptide subunits. It belongs
to the integrin receptor family, which includes a 400-kDa
α heavy chain and two 200-kDa light chains designated β 1
and β 2. By electron microscopy the molecule is arranged
in the form of a cross. The domain structures of the α
and β chains resemble one another. There are six primary
domains. Domains I and II have repeat sequences forming
α helices. Domains III and V are composed of cysteine-rich
NH 3 +
Collagen IB
binding site
β1 Chain
(215kD)
– OOC
1
NH 3 +
Laminin.
COO –
α Chain
(400kD)
β2 Chain
(205kD)
COO –
Heparan sulfate
proteoglycan
binding site
NH 3 +
Lamina propria.
repeating sequences. The globular regions are composed
of domains IV and VI. An additional short cysteine-rich
α domain is located between the I and II domains in the
β 1 chain. A relatively large globular segment is linked to
the C terminal of domain I, designated the “foot” in the
α chain. Five “toes” on the foot contain repeat sequences.
Laminins have biological functions and characteristics that
include facilitation of cellular adhesion and linkage to other
basement membrane constituents such as collagen type IV,
heparan, and glycosaminoglycans. Laminins also facilitate
neurite regeneration, an activity associated with the foot
of the molecule. Each form of laminin represents different
gene products, although they possess a high degree of
homology. S laminin describes a form found only in synaptic
and nonmuscle basal lamina. Its is a single 190-kDa
polypeptide (in reduced form) and its weight is >1000 kDa
in the nonreduced form. It is associated with the development
or stabilization of synapses and is homologous to the
β 1 chain of laminin. Laminin facilitates cell attachment and
migration, plays a role in differentiation and metastasis, and
is produced by macrophages, endothelial cells, epithelial
cells, and Schwann cells.
laminin receptor
A membrane protein composed of two disulfide bondlinked
subunits, one relatively large and one relatively
small. Its function appears to be the attachment of cells.
It may share structural similarities with fibronectin and
vitronectin, both of which are also integrins.
Karl Landsteiner.