Biomedical subjects

M F Champliaud

Publications and source records attributed to M F Champliaud.

21 records · Page 2Linked to original sources

PubMed1994

The 100-kDa chain of nicein/kalinin is a laminin B2 chain variant.

We have isolated the basement membrane component nicein and performed rotary-shadow analyses using electron microscopy that showed the presence of two forms (I and II) of the protein. Molecular cloning of the cDNA that codes for the 100-kDa chain of the protein revealed that the sequence matches those independently identified for the 105-155-kDa subunit of kalinin, a recently identified basement membrane component. These data demonstrate that nicein and kalinin contain an identical chain. The length of the open reading frame in the cDNA (approximately 5200 nucleotides) and amino acid sequence obtained from the N-terminus of the 105-kDa kalinin chain showed the occurrence of a precursor polypeptide. This immature polypeptide is probably related to form I, observed by rotary shadowing, while the mature form is related to form II. It is noteworthy that nicein/kalinin subunits share discrete sequence similarities with the B2 chain of human laminin, but with a cleavage occurring within domain III that eliminates domains IV and V from the final product. The sequence of this subunit is nearly identical to that of B2t, a recently described polypeptide supposed to be related to a new laminin variant. Since nicein/kalinin expression is specifically impaired in the severe genodermatosis Herlitz junctional epidermolysis bullosa, the role and structure of this tissue-restricted laminin variant is crucial for the understanding of epidermal-dermal adhesion.

Amino Acid Sequence↗

PubMed1994

Interactions between cells and collagen V molecules or single chains involve distinct mechanisms.

Acid-soluble and pepsin-treated collagen V were prepared from fetal human bones or human placenta, respectively, to be tested for potential cell adhesion promoting activity. Out of 14 different collagen I-adhering cell lines, 10 showed distinct adhesion to collagen V. In all cases adhesion was followed by spreading. The activities of intact and pepsin-solubilized collagen V were similar, suggesting that the cell binding sites are restricted to the triple-helical domain of the molecules. Cell adhesion was also induced by the unfolded form of collagen V and after separation of the alpha chains by heparin affinity chromatography. Isolated alpha 2(V) chains, rich in RGD sequences, were more efficient than isolated alpha 1(V) chains. However, cell adhesion to native or denatured collagen V did not proceed by the same molecular mechanisms as shown by cell adhesion inhibition experiments. Cell adhesion to native collagen V was insensitive to the presence of RGD-containing synthetic peptides while adhesion to denatured collagen V was inhibited by the peptides. Furthermore, the results strongly suggested a major role for alpha 1 beta 1 and alpha 2 beta 1 integrins in the RGD-independent cell adhesion to native collagen V. These data indicate that collagen V is a specific adhesive substrate for different cell types. It also suggests that distinct sets of RGD-dependent and RGD-independent receptors mediate cell attachment to unfolded and native collagen V, respectively. This mechanism is shared by at least the interstitial collagens I and VI, which supports the hypothesis that when included in the triple-helical conformation of collagens, RGD sequences are either not accessible to cells or exhibit specific conformations recognized by different integrins.

Actins↗

PubMed1990

Fibril-associated collagens.

Many collagen fibrils have been shown to be heterotypic, i.e. composed of more than one collagen type. Fibrils containing type I collagen as the major constituent do also contain, at least in some tissues, type III and type V collagens. Fibrils containing type II collagen have been shown to also contain type XI collagen. The type I, II, III, V and XI collagen molecules are very similar and are clearly derived from a single ancestral gene. However their processings are not identical. While collagen types I and II have a N-propeptide which is cleaved for their insertion in the fibrils, collagen types V and XI keep a N-terminal extension which must include, based on the cDNA derived structures, a short triple helix and a globular domain. They are thought to contribute to the control of fibril lateral growth and diameter. Other collagens are associated with fibrils without having the long triple uninterrupted triple helix characteristic of collagen types I, II, III, V and XI. Type IX collagen has been shown to be covalently cross-linked to type II collagen and to lay at or near the surface of fibrils, with a triple helical arm projecting in the extrafibrillar space a globular N-terminal domain. Type XII collagen is found in type I collagen containing matrices and contains a triple helical domain homologous to the type IX COL1 domain. This suggests a similar function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗