Teaming up synthetic chemistry and histochemistry for activity screening in galectin-directed inhibitor design.
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.
['Roy|René|R|', 'Cao|Yihong|Y|', 'Kaltner|Herbert|H|', 'Kottari|Naresh|N|', 'Shiao|Tze Chieh|TC|', 'Belkhadem|Karima|K|', 'André|Sabine|S|', 'Manning|Joachim C|JC|', 'Murphy|Paul V|PV|', 'Gabius|Hans-Joachim|HJ|']
D005434:Flow Cytometry D037161:Galectins D006027:Glycosides D006801:Humans D037102:Lectins D011485:Protein Binding
Lectin Glycoprotein Glycocluster Agglutinin Glycosylation