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Isolation and Partial Characterisation of Insulin-Mimetic Inositol Phosphoglycans from Human Liver

Isolation and Partial Characterisation of Insulin-Mimetic Inositol Phosphoglycans from Human Liver

Authors :
Yolanda León
Matías A. Avila
Hugo Norberto Caro
Isabel Varela-Nieto
Sirilaksana Kunjara
David R. Jones
Thomas W. Rademacher
Source :
Digital.CSIC. Repositorio Institucional del CSIC, instname
Publication Year :
1997
Publisher :
Elsevier BV, 1997.

Abstract

Extracts of human liver were found to contain activities which copurified and coeluted with the two major subtypes of mediators (type A and type P) isolated from insulin-stimulated rat liver. The putative type A mediator from human liver inhibited cAMP-dependent protein kinase from bovine heart, decreased phosphoenolpyruvate carboxykinase mRNA levels in rat hepatoma cells, and stimulated lipogenesis in rat adipocytes. The putative type P mediator stimulated bovine heart pyruvate dehydrogenase phosphatase. Both fractions were able to stimulate proliferation of EGFR T17 fibroblasts and the type A was able to support growth in organotypic cultures of chicken embryo cochleovestibular ganglia. Both activities were resistant to Pronase treatment and the presence of carbohydrates, phosphate, and free-amino groups were confirmed in the two fractions. These properties are consistent with the structure/function characteristics of the type A and P inositolphosphoglycans (IPG) previously characterized from rat liver. Further, the ability of the human-derived mediators to interact with rat adipocytes and bovine-derived metabolic enzymes suggests similarity in structure between the mediators purified from different species. Galactose oxidase-susceptible membrane- associated glycosylphosphatidylinositols (GPI) have been proposed to be the precursors of IPG. GPI was purified from human liver membranes followed by treatment with galactose oxidase and reduction with NaB3H4. Serial t.l.c. revealed three radiolabeled bands which comigrated with the putative GPI precursors found in rat liver. These galactose-oxidase-reactive lipidic compounds, however, were only partially susceptible to hydrolysis with phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis and were resistant to glycosylphosphatidylinositol-specific phospholipase C from Trypanosoma brucei. These data indicate that IPG molecules with insulin-like biological activities are present in human liver.<br />This work was supported by the Acción Integrada Hispano-Británica, by grants from the Medical Research Council, the Jules Thorn Trust, and the British Council to T.W.R. and Dirección General de Investigación, Ciencia y Tecnologı́a (DGICYT), Comunidad de Madrid, and Europharma (Boehringer Ingelheim group) to I.V-N. H.N.C. and S.K. are supported by the Medical Research Council (UK). Y.L. and M.A.A. are supported by Ministerio de Educación y Ciencia (Spain) and D.R.J. by The Royal Society (UK) and the Consejo Superior de Investigaciones Cientı́ficas (Spain).

Details

ISSN :
10773150
Volume :
61
Database :
OpenAIRE
Journal :
Biochemical and Molecular Medicine
Accession number :
edsair.doi.dedup.....1e26bb887aa1905ec47194208e8d050b
Full Text :
https://doi.org/10.1006/bmme.1997.2607