Radioimmunoassays for circulating basement membrane proteins: Laminin und 7 S collagen

Extracellular matrix and neuronal movement

During brain development, both neuronal migration and axon guidance are influenced by extracellular matrix molecules present in the environment of the migrating neuronal cell bodies and nerve fibers. Glial laminin is an extracellular matrix protein which these early brain cells preferentially attach to. Extracellular glycosaminoglycans are suggested to function in restricting neuronal cell bodies and axons from certain brain areas. Since laminin is deposited along the radial glial fibers and along the developing nerve pathways in punctate form, the punctate assemblies may be one of the key factors in routing the developing neurons in vivo. This review discusses the role of laminin in neuronal movement given the present concept of the extracellular matrix molecules and their proposed interactions.

Identification of a neurite outgrowth-promoting domain of laminin using synthetic peptides

We have identified a synthetic peptide derived from the B2-chain of mouse laminin, Arg-Asn-Ile-Ala-Glu-Ile-Ile-Lys-Asp-Ile (p20), which stimulates the neurite outgrowth-promoting activity of the native molecule. In organotypic cultures, neurons from newborn mouse brain or embryonic peripheral nervous system responded by extensive neurite outgrowth for native laminin or the peptide p20 in the culture medium. If rat cerebellar neurons were grown on laminin, 1-5 microM (1-5 micrograms/ml) of peptide p20 in the culture medium competed with laminin and inhibited neuronal attachment and neurite outgrowth, whereas higher concentrations (greater than 50 microM; greater than 50 micrograms/ml) had a specific neurotoxic effect. When peptide p20 was used as the culture substratum, neurite outgrowth in cerebellar cultures was up to 60% of that seen on native laminin. Our results indicate that a neurite outgrowth-promoting domain of laminin is located in the alpha-helical region of the B2-chain, and is active for both central and peripheral neurons.

Serum concentrations of laminin and aminoterminal propeptide of type III procollagen in relation to the portal venous pressure of fibrotic liver diseases

In sera of patients with fibrotic liver diseases (n = 33) classified histologically into various degrees of liver fibrosis (n = 21) and cirrhosis (n = 12) the concentrations of the basement membrane protein laminin and of its pepsinresistant fragment P1 and of the N-terminal propeptide of type III procollagen were determined. The concentrations of both proteins were related to the portal venous pressure measured in these patients. Compared with the reference population (n = 146) the concentration of laminin increases from 1.04 U/ml (normal persons) to 1.69 +/- 0.46 U/ml in liver fibrotic and 2.58 +/- 0.87 U/ml in liver cirrhotic patients. Although the concentrations of the propeptide of type III procollagen increase also there exist only weak correlations between both connective tissue proteins in serum. Laminin is correlated highly positive with the portal venous pressure in cirrhotic subjects (r = 0.9206), the extent of laminin elevation reflects closely the degree of portal hypertension. Virtually all of the fibrotic patients having a laminin concentration within the reference range had a normal portal venous pressure. The data suggest laminin as a potentially useful parameter for monitoring the portal venous pressure in cirrhotic and severe fibrotic patients.

Serum laminin--its concentration increases with portal hypertension in cirrhotic liver disease

The concentrations in serum of the high molecular weight glycoprotein laminin and of the N-terminal propeptide of type III procollagen were determined in various histologically proven fibrotic liver diseases (n = 33), of which the portal venous pressure has been measured indirectly. The concentrations of both biomatrix proteins were related to the portal venous pressure. Laminin in serum of normal persons (n = 146) ranged from 0.81 to 1.43 U/ml. Compared with the mean normal concentration (1.04 U/ml) the glycoprotein is increased in fibrotic liver lesions in parallel with the severity of the fibrotic organ transformation reaching the highest values (2.58 +/- 0.87 U/ml, P less than 0.001) in liver cirrhosis (n = 12). The level of N-terminal propeptide of type III procollagen increased similarly, but the concentrations of both matrix proteins exhibit only weak statistical correlations (r = 0.6680). The level of laminin is correlated strongly with the elevation of the portal venous pressure in cirrhotic (r = 0.9206) and fibrotic (r = 0.7157) subjects. For the propeptide of procollagen the respective correlation is r = 0.4808. Molecular sieve chromatography reveals a heterogeneous composition of laminin-related antigens in serum with two main molecular weight fractions of 700 and 300 kD, respectively.

7 S collagen: a method for the measurement of serum concentrations in man

A radioimmunoassay was developed for the detection of 7 S collagen, a basement membrane component derived from type IV collagen, in sera of patients. Two forms of 7 S collagen were isolated by limited collagenase digestion of type IV collagen from bovine placenta. Antisera against both forms were raised in rabbits. The antigens were labeled by conjugation with the Bolton Hunter reagent or by the Chloramine T method. Free and bound antigen were separated using a second antibody directed against rabbit-IgG. Serum concentrations of 7 S collagen ranged from 5-14 micrograms/l. Serum levels of 7 S collagen were increased in diabetic patients as compared to normal subjects.