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Determination of structural and functional overlap/divergence of five proto‐type galectins by analysis of the growth‐regulatory interaction with ganglioside GM 1 in silico and in vitro on human neuroblastoma cells
Author(s) -
André Sabine,
Kaltner Herbert,
Lensch Martin,
Russwurm Roland,
Siebert HansChristian,
Fallsehr Christine,
Tajkhorshid Emad,
Heck Albert J.R.,
von Knebel Doeberitz Magnus,
Gabius HansJoachim,
Kopitz Juergen
Publication year - 2004
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.20699
Subject(s) - galectin , in silico , ganglioside , biology , divergence (linguistics) , type (biology) , computational biology , biochemistry , gene , ecology , philosophy , linguistics
The growth‐regulatory interplay between ganglioside GM 1 on human SK‐N‐MC neuroblastoma cells and an endogenous lectin provides a telling example for glycan (polysaccharide) functionality. Galectin‐1 is the essential link between the sugar signal and the intracellular response. The emerging intrafamily complexity of galectins raises the question on defining extent of their structural and functional overlap/divergence. We address this problem for proto‐type galectins in this system: ganglioside GM 1 as ligand, neuroblastoma cells as target. Using the way human galectin‐1 interacts with this complex natural ligand as template, we first defined equivalent positioning for distinct substitutions in the other tested proto‐type galectins, e.g., Lys63 vs. Leu60/Gln72 in galectins‐2 and ‐5. As predicted from our in silico work, the tested proto‐type galectins have affinity for the pentasaccharide of ganglioside GM 1 . In contrast to solid‐phase assays, cell surface presentation of the ganglioside did not support binding of galectin‐5, revealing the first level of regulation. Next, a monomeric proto‐type galectin (CG‐14) can impair galectin‐1‐dependent negative growth control by competitively blocking access to the shared ligand without acting as effector. Thus, the quaternary structure of proto‐type galectins is an efficient means to give rise to functional divergence. The identification of this second level of regulation is relevant for diagnostic monitoring. It might be exploited therapeutically by producing galectin variants tailored to interfere with galectin activities associated with the malignant phenotype. Moreover, the given strategy for comparative computational analysis of extended binding sites has implications for the rational design of galectin‐type‐specific ligands. © 2004 Wiley‐Liss, Inc.