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Teaming up synthetic chemistry and histochemistry for activity screening in galectin-directed inhibitor design

Authors
  • Roy, René1
  • Cao, Yihong1
  • Kaltner, Herbert2
  • Kottari, Naresh1
  • Shiao, Tze Chieh1
  • Belkhadem, Karima1
  • André, Sabine2
  • Manning, Joachim C.2
  • Murphy, Paul V.3
  • Gabius, Hans-Joachim2
  • 1 University du Québec à Montréal, Pharmaqam and Nanoqam, Department of Chemistry, P.O. Box 8888, Succ. Centre-Ville, Montreal, QC, H3C 3P8, Canada , Montreal (Canada)
  • 2 Ludwig-Maximilians-University Munich, Faculty of Veterinary Medicine, Institute of Physiological Chemistry, Veterinärstr. 13, Munich, 80539, Germany , Munich (Germany)
  • 3 National University of Ireland Galway, School of Chemistry, University Road, Galway, Ireland , Galway (Ireland)
Type
Published Article
Journal
Histochemistry and Cell Biology
Publisher
Springer Berlin Heidelberg
Publication Date
Dec 24, 2016
Volume
147
Issue
2
Pages
285–301
Identifiers
DOI: 10.1007/s00418-016-1525-5
Source
Springer Nature
Keywords
License
Yellow

Abstract

A hallmark of endogenous lectins is their ability to select a few distinct glycoconjugates as counterreceptors for functional pairing from the natural abundance of cellular glycoproteins and glycolipids. As a consequence, assays to assess inhibition of lectin binding should necessarily come as close as possible to the physiological situation, to characterize an impact of a synthetic compound on biorelevant binding with pharmaceutical perspective. We here introduce in a proof-of-principle manner work with sections of paraffin-embedded tissue (jejunum, epididymis) and labeled adhesion/growth-regulatory galectins, harboring one (galectin-1 and galectin-3) or two (galectin-8) types of lectin domain. Six pairs of synthetic lactosides from tailoring of the headgroup (3′-O-sulfation) and the aglycone (β-methyl to aromatic S- and O-linked extensions) as well as three bi- to tetravalent glycoclusters were used as test compounds. Varying extents of reduction in staining intensity by synthetic compounds relative to unsubstituted/free lactose proved the applicability and sensitivity of the method. Flanking cytofluorimetric assays on lectin binding to native cells gave similar grading, excluding a major impact of tissue fixation. The experiments revealed cell/tissue binding of galectin-8 preferentially via one domain, depending on the cell type so that the effect of an inhibitor in a certain context cannot be extrapolated to other cells/tissues. Moreover, the work with the other galectins attests that this assay enables comprehensive analysis of the galectin network in serial tissue sections to determine overlaps and regional differences in inhibitory profiles.

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