Chemistry Reference
In-Depth Information
19.3
Lectin Ligands and Affi nity Regulation
Purifi cation of tissue lectins, often using affi nity chromatography as a crucial step
(please see Chapter 15.3 for its introduction to lectin research and Chapter 18.3 for
further practical details), and also their labeling, as similarly done with plant lectins,
were thus crucial to trace endogenous ligands. The range of functions presented
in Table 19.2 intimates a correlation between certain lectins and their targets,
sometimes already refl ected in lectin names. A lysosomal enzyme will present the
epitope with mannose - 6 - phosphate as the postal code for P - type - lectin - mediated
transfer to its fi nal destination, and mannan on the cell surface, a characteristic of
the mannose-rich glycophenotype of yeast cells, is a high-affi nity matrix for the
mannan (or mannose)-binding lectin [9, 10]. Functions in cell adhesion and growth
or mediator release call for particular sets of glycoligands in the respective context.
The summary of currently known binding partners for two multifunctional galec-
tins lists glycoconjugates known for adhesion and cell signaling capacities (Table
19.3). From the wide array of cell-surface glycoconjugates, a tissue lectin is capable
of selecting a few binding partners. For example, interaction with the extracellular
matrix glycoproteins fi bronectin and laminin can modulate adhesion (here a galec-
tin acts as a nonintegrin receptor), binding to CD7 or ganglioside GM1 initiates
Table 19.3
Cellular glycoconjugates and proteins as ligands for endogenous lectins: case study
of galectins - 1 and - 3.
Type of ligand
Galectin - 1
Galectin - 3
Glycan
Ovarian carcinoma antigen CA125,
CD2, CD3, CD4, CD7, CD43,
CD45, CD95, carcinoembryonic
antigen, fi bronectin (tissue), gas-
trointestinal mucin, hsp90-like
glycoprotein,
CD7, CD11b of CD11b/CD18 (Mac-1
antigen, CR3), CD13 (aminopeptidase
N), CD32, CD43, CD45, CD66a,b, CD71,
CD95, CD98, carcinoembryonic antigen,
colon cancer mucin and MUC1-D (
N
-
glycan at Asn36), cubilin, C4.4A (mem-
ber of Ly6 family), epidermal growth
factor receptor, haptoglobin
α
1
/
α
4
/
α
5
/
α
7
β
1
-
and
α
7
- in tegrins, cell adhesion mol-
ecule L1, laminin, lamp - 1, Mac - 2 -
bind ing protein, nephrin, neuro-
pilin - 1, rece p tor protein-tyrosine
phosphatase (RPTP
4
β
- subunit
(after desialylation), hensin (DMBT-1),
glycoform of IgE,
β
β
1
- integrin
(CD29)
), thrombos-
pondin, Thy-1, tissue plasminogen
activator, chondroitin sulfate pro-
teoglycan, distinct neutral glycolip-
ids, ganglioside GM1
β
and
1
- integrin, LI - cadherin, laminin,
lamp - 1/ - 2, Mac - 2 - binding protein, Mac -
3, MAG, MP20 (tetraspanin), NG2 pro-
teoglycan, T cell receptor complex,
tenascin, tissue plasminogen activator,
transforming growth factor -
α
4
β
β
receptor,
ganglioside GM1
Protein
Gemin4, oncogenic H - Ras, OCA -
B, pre-B cell receptor (human, not
murine system)
AGE products, Alix/AIP - 1, ATP synthase
b-subunit, axin, bcl - 2,
- catenin, Cys/His -
rich protein, Gemin4, hnRNPQ, mSufu,
nucling, oncogenic K - Ras, OCA - B, pCIP,
PIAS1, synexin (annexin VII), TTF-1
β
