| 1. |
- Banerjee, Meenal, et al.
(författare)
-
Proliferation and plasticity of human beta cells on physiologically occurring laminin isoforms
- 2012
-
Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207 .- 1872-8057. ; 355:1, s. 78-86
-
Tidskriftsartikel (refereegranskat)abstract
- We have previously characterized the molecular composition of human islet basement membranes and shown that human beta cells bind to laminin 511 (LM511) through integrin alpha 3 beta 1 and Lutheran glycoprotein. We have now investigated the impact of physical contact between cultured human beta cells and the laminin isoforms occurring in their natural niche. Human islet preparations derived from 15 donors were used, beta cells and duct cells were purified by magnetic sorting. Overall beta-cell proliferation was low or undetectable. However, in many experiments the only proliferating beta cells were detected in contact with the laminin isoforms that are found in the human islets in vivo (511 and 411). Purified ductal and beta cells underwent epithelial-mesenchymal transition (EMT). LM511 partially blocked this dedifferentiation of purified beta cells, and did not affect purified duct cells. Interactions with the surrounding basement membrane are important for the growth and function of human beta cells. However, only a very limited level of beta-cell proliferation can be induced by exogenous factors. LM511 may be a useful substrate for human beta-cell maintenance in vitro.
|
|
| 2. |
- Li, Jin-Ping, et al.
(författare)
-
Biosynthesis of heparin / heparan sulfate : cDNA cloning and expression of D-glucuronyl C5-epimerase from bovine lung
- 1997
-
Ingår i: Journal of Biological Chemistry. - : Elsevier BV. - 0021-9258 .- 1083-351X. ; 272:44, s. 28158-28163
-
Tidskriftsartikel (refereegranskat)abstract
- Glucuronyl C5-epimerases catalyze the conversion of D-glucuronic acid (GlcUA) to L-iduronic acid (IdceA) units during the biosynthesis of glycosaminoglycans. An epimerase implicated in the generation of heparin/heparan sulfate was previously purified to homogeneity from bovine liver (Campbell, P., Hannesson, H. H., Sandbäck, D., Rodén, L., Lindahl, U., and Li, J.-p. (1994) J. Biol. Chem. 269, 26953-26958). The present report describes the molecular cloning and functional expression of the lung enzyme. The cloned enzyme contains 444 amino acid residues and has a molecular mass of 49,905 Da. N-terminal sequence analysis of the isolated liver enzyme showed this species to be a truncated form lacking a 73-residue N-terminal domain of the deduced amino acid sequence. The coding cDNA insert was cloned into a baculovirus expression vector and expressed in Sf9 insect cells. Cells infected with recombinant epimerase showed a 20-30-fold increase in enzyme activity, measured as release of 3H2O from a polysaccharide substrate containing C5-3H-labeled hexuronic acid units. Furthermore, incubation of the expressed protein with the appropriate (GlcUA-GlcNSO3)n substrate resulted in conversion of approximately 20% of the GlcUA units into IdceA residues. Northern analysis implicated two epimerase transcripts in both bovine lung and liver tissues, a dominant approximately 9-kilobase (kb) mRNA and a minor approximately 5-kb species. Mouse mastocytoma cells showed only the approximately 5-kb transcript. A comparison of the cloned epimerase with the enzymes catalyzing an analogous reaction in alginate biosynthesis revealed no apparent amino acid sequence similarity.
|
|
