Research and
development


Galectins

To date, 14 types of mammalian galectins are known including galectins-1 to -15.1 Because of the lack of human counterparts of galectins-5, -6, -14, and -15, there are 10 types of human galectins, although the number may increase in the future. Galectins are classified into three major subgroups on the basis of their structures (Figure 1, Table 1). The first group consists of proto-type galectins with one carbohydrate binding domain2 or carbohydrate recognition domain (CRD). The second group consists of chimera-type galectins that have one CRD and another non-carbohydrate-binding domain linked together. The third group consists of tandem-repeat-type galectins with two CRDs. Although proto-type and chimera-type galectins have only one CRD, two molecules bind to each other (dimerization) so that they can actually bind to two carbohydrate chains as tandem-repeat-type galectins do (some proto-type galectins are unlikely to form a dimer).

Table 1. Characteristics and functions of mammalian galectin family.
@@@ Type* Tissue distribution

Functions and others

Galectin-1 P Ubiquitous expression

Apoptosis induction in activated T cells
Cell growth, mRNA splicing
Regeneration of nerve axon (oxidized galectin-1)
Aberrant neurite outgrowth of the olfactory neuron**

Galectin-2 P Small intestine, stomach Risk factor of myocardial infarction
Galectin-3 C Ubiquitous expression

cell adhesion, mRNA splicing
Inhibition of T cell apoptosis
Macrophage chemotactic factor
AGE receptor
Reduced intraperitoneal inflammatory response**
Accelerated progression of diabetic nephropathy**

Galectin-4 T Gastrointestinal tract Activation of intestinal CD4+ T cells
Galectin-5 P Erythrocytes (rat)

Erythroblast maturation?
High homology to the C-terminal CRD of galectin-9

Galectin-6 T Gastrointestinal tract (mouse) High homology to galectin-4
Galectin-7 P

Keratinocytes (stratified epithelium)

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Galectin-8 T Ubiquitous expression

Cell adhesion
Regulation of neutrophil function

Galectin-9 T

Immune cells, lung, gastrointestinal tract

Apoptosis induction in activated T cells
Eosinophil chemotactic factor
Apoptosis induction in cancer cells
Cell adhesion

Galectin-10 P Eosinophils, basophils

Charcot-Leyden crystal
Affinity for mannose

OVGAL11 P

Sheep stomach with parasitic infection

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Galectin-12 T Adipose tissue Apoptosis induction in adipocytes
Galectin-13 P Placenta

Pregnancy-related protein
High homology to galectin-10

Galectin-14 P Eosinophils (sheep)

Possible involvement in allergic reaction?
Relatively high homology to the N-terminal CRD of galectin-9

Galectin-15/
OVGAL11

P

Sheep stomach with parasitic infection
Uterus

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* P, proto-type; C, chimera-type; T, tandem-repeat-type
** Phenotype of knockout mice

Note 1: There are some inconsistencies in the nomenclature of mammalian galectins. In 2000, Dunphy et al. identified a new galectin as a substance that was upregulated in sheep stomachs with parasitic infections. Although 10 types of mammalian galectins (galectins-1 to -10) were known at that time, Dunphy et al. named the new galectin OVGAL11 and did not use the term ggalectin-11.h In 2001, Yang et al. and Hotta et al. reported a new galectin specifically expressed in adipocytes and named galectin-12. Their articles indicate that these two groups regarded OVGAL11 as galectin-11. In 2004, however, Gray et al. reported the expression of OVGAL11 in sheep uterus (endometrium and trophectoderm) and its potential function in the uterus in an article, and arbitrarily designated OVGAL11 as galectin-15. It was careless of Gray and others not to know that researchers working on galectins generally regarded OVGAL11 as galectin-11.

Dunphy JL, Balic A, Barcham GJ, Horvath AJ, Nash AD, Meeusen EN.
Isolation and characterization of a novel inducible mammalian galectin.
J Biol Chem. 2000 Oct 13;275(41):32106-13.

Yang RY, Hsu DK, Yu L, Ni J, Liu FT.
Cell cycle regulation by galectin-12, a new member of the galectin superfamily.
J Biol Chem. 2001 Jun 8;276(23):20252-60.

Hotta K, Funahashi T, Matsukawa Y, Takahashi M, Nishizawa H, Kishida K, Matsuda M, Kuriyama H,
Kihara S, Nakamura T, Tochino Y, Bodkin NL, Hansen BC, Matsuzawa Y.
Galectin-12, an Adipose-expressed Galectin-like Molecule Possessing
Apoptosis-inducing Activity.
J Biol Chem. 2001 Sep 7;276(36):34089-97.

Gray CA, Adelson DL, Bazer FW, Burghardt RC, Meeusen EN, Spencer TE.
Discovery and characterization of an epithelial-specific galectin in the
endometrium that forms crystals in the trophectoderm.
Proc Natl Acad Sci U S A. 2004 May 25;101(21):7982-7.

Note 2: Domain is a portion of a protein with its own specific structure or function.
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