title: Determination of structural and functional overlap/divergence of five proto-type galectins by analysis of the growth-regulatory interaction with ganglioside GM1 in silico and in vitro on human neuroblastoma cells.
abstract: The growth-regulatory interplay between ganglioside GM1 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 GM1 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 GM1. 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.
authors.affiliation: Institut für Physiologische Chemie, Tierärztliche Fakultät, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: André
authors.forename: Herbert
authors.initials: H
authors.lastname: Kaltner
authors.forename: Martin
authors.initials: M
authors.lastname: Lensch
authors.forename: Roland
authors.initials: R
authors.lastname: Russwurm
authors.forename: Hans-Christian
authors.initials: HC
authors.lastname: Siebert
authors.forename: Christine
authors.initials: C
authors.lastname: Fallsehr
authors.forename: Emad
authors.initials: E
authors.lastname: Tajkhorshid
authors.forename: Albert J R
authors.initials: AJ
authors.lastname: Heck
authors.forename: Magnus
authors.initials: M
authors.lastname: von Knebel Doeberitz
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Gabius
authors.forename: Juergen
authors.initials: J
authors.lastname: Kopitz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D005677:G(M1) Ganglioside / Q000378:metabolism*; D037483:Galectin 1 / Q000378:metabolism; D037501:Galectin 2 / Q000378:metabolism; D037502:Galectin 3 / Q000378:metabolism; D037541:Galectin 4 / Q000378:metabolism; D037161:Galectins / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014407:Tumor Cells, Cultured
chemical_list: D037483:Galectin 1; D037501:Galectin 2; D037502:Galectin 3; D037541:Galectin 4; D037161:Galectins; D008024:Ligands; C092501:galectin 5; D005677:G(M1) Ganglioside