Author Topic: The Laminin Protein Chain and N-acetylneuraminic acid  (Read 6047 times)

Offline JC Spencer

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The Laminin Protein Chain and N-acetylneuraminic acid
« Reply #1 on: May 26, 2008, 10:53:03 PM »
Comments by J. C. Spencer
LAMININ has been causing some rather interesting chatter on the internet lately.  Before I heard the chatter, I reported on a paper I wrote in 1996 about the glue that holds the human cells together and without it there is aging, disease, and death. The laminin protein chains give a design that accounts for a lot of its flexibility in connecting up various kinds of molecules.  Because of this, scientists are extremely interested in the whole family of laminins. They are a family of glycoproteins that are an integral part of the structural scaffolding in almost every human cell.

I do not object to the chatter on the internet about laminin and its shape.  Though interesting, I do not get excited about its shape as I do about what it does and how without it we would not know life as we do.  (You can view laminin in our NEWS section under Featured Articles on the Science of Glycomics.)  Of course, it is the shape that makes it all possible.

The abstract below from a science paper out of France shows how the sugar N-acetylneuraminic acid also known as sialic acid aids the immune system.  Without this assistance the immune system would not be strong enough to fight off the fungal conidia.

Sialic acid-dependent recognition of laminin and fibrinogen by Aspergillus fumigatus conidia

JP Bouchara, M Sanchez, A Chevailler, A Marot-Leblond, JC Lissitzky, G Tronchin and D Chabasse
Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, Angers, France.

In an attempt to define the molecular basis of the adherence of Aspergillus fumigatus conidia to the host tissues, a step which might be mediated by the recognition of basement membrane laminin or fibrinogen, we analyzed the binding of these glycoproteins by flow cytometry and a microtiter plate adherence assay. Flow cytometry revealed that the binding of fluorescein isothiocyanate-labeled laminin to conidia was saturable and specific. Moreover, the ability of conidia to bind laminin increased with their maturation. Competition experiments showed a cross-reactivity between laminin and fibrinogen binding and a lack of interactions with glycosaminoglycans. In addition, the binding of laminin was not inhibited by the different adhesive synthetic peptides tested. Furthermore, the microtiter plate assay of adherence to chymotrypsin degradation products of laminin or fibrinogen purified by gel filtration suggested a unique binding site common to sequential degradation fragments or the presence of multiple binding sites on the two ligands. Therefore, the role of carbohydrates in the recognition process was investigated. Among the carbohydrates tested, constitutive of the conidial wall or of the oligosaccharide side chains of laminin and fibrinogen, only N-acetylneuraminic acid and sialyllactose inhibited the binding of these glycoproteins to conidia. In conclusion, these results strengthen the idea that the laminin and fibrinogen receptors in A. fumigatus are identical and suggest an interaction mediated by a sialic acid-specific lectin of the conidial wall.

Infect. Immun., Jul 1997, 2717-2724, Vol 65, No. 7
Copyright © 1997, American Society for Microbiology
« Last Edit: May 27, 2008, 08:32:34 PM by JC Spencer »