http://www.jbc.org/content/254/19/9933.full.pdf

Laminin--a glycoprotein from basement membranes.

We have studied the reconstitution of basement membrane molecules from extracts prepared from the basement membrane of the EHS tumor. Under physiological conditions and in the presence of added type IV collagen and heparan sulfate proteoglycan, gellike structures form whose ultrastructure appears as interconnected thin sheets resembling the lamina dense zone of basement membrane. The major components of the reconstituted structures include laminin, type IV collagen, heparan sulfate proteoglycan, entactin, and nidogen. These components polymerize in constant proportions on reconstitution, suggesting that they interact in defined proportions. Molecular sieve studies on the soluble extract demonstrate that laminin, entactin, and nidogen are associated in large but dissociable complexes which may be a necessary intermediate in the deposition of basement membrane. The reconstituted matrix was biologically active and stimulated the growth and differentiation of certain cells.

Basement Membrane Complexes with Biological Activity

How does the extracellular matrix direct gene expression

We have studied the extractability of type IV collagen, laminin, and heparan sulfate proteoglycan from EHS tumor tissue growth in normal and lathyritic animals. Laminin and heparan sulfate proteoglycan were readily extracted with chaotropic solvents from both normal and lathyritic tissue. The collagenous component was only solubilized from lathyritic tissue in the presence of a reducing agent. These results indicate that lysine-derived cross-links and disulfide bonds stabilize the collagenous component in the matrix but not the laminin or the heparan sulfate proteoglycan. The majority of the collagen present in the extracts had a native triple helix based upon the pattern of peptides resistant to pepsin digestion and visualization in the electron microscope by the rotary shadow technique. This protein was composed of chains (Mr 185000 and 170000) identical in migration to the chains of newly synthesized type IV procollagen. This finding confirms earlier work that indicates that the biosynthetic form, type IV procollagen, is incorporated as such in the basement membrane matrix. Material with smaller chains (Mr 160000 and 140000) appeared on storage in acetic acid solutions. These results indicate that the lower molecular weight collagen in acid extracts of basement membrane arises artifactually due to an endogenous acid-active protease.

Isolation and characterization of type IV procollagen, laminin, and heparan sulfate proteoglycan from the EHS sarcoma.

CONTENTS INTRODUCTION.. .• .••.....• .•••.. 57 STRUCTURE 58 INTERACTIONS WITH OTHER BASEMENT MEMBRANE PROTEINS ......•• 65 BIOSYNTHESIS AND REGULATION •.•....• • • 69 CELL BINDING AND OTHER BIOLOGICAL PROPERTIES OF LAMININ 71 MOLECULAR MODELS OF BASEMENT MEMBRANE STRUCTURE •.. 76

Laminin and Other Basement Membrane Components

Properties of a basement membrane-related glycoprotein synthesized in culture by a mouse embryonal carcinoma-derived cell line

A novel extracellular membrane elaborated by a mouse embryonal carcinoma-derived cell line.

Biosynthesis and partial characterization of tear film glycoproteins. Incorporation of radioactive precursors by human lacrimal gland explants in vitro.

The effect of age on the compositional analysis of human Descemet’s membrane was examined. Membranes were obtained from human corneas ranging from 0.5 to 95 years and purified by sodium dodecyl sulfate (SDS) extraction. Substantial age-related changes were obtained in the amino acid compositions of the SDS-insoluble basement membranes. These results suggested that compositional changes occur during the aging process, which appeared to reflect an alteration in the subunit make-up of the basement membrane.

Ian L. Freeman

Papers

Properties of a basement membrane-related glycoprotein synthesized in culture by a mouse embryonal carcinoma-derived cell line

A novel extracellular membrane elaborated by a mouse embryonal carcinoma-derived cell line.

Biosynthesis and partial characterization of tear film glycoproteins. Incorporation of radioactive precursors by human lacrimal gland explants in vitro.

Age-Related Biochemical Changes in Human Descemet’s Membrane

An accelerated, improved single-column procedure for the amino acid analysis of basement membrane and collagen-like proteins