Galectin-1 is involved in the potentiation of neuropathic pain in the dorsal horn

Galectin-1 is one of the endogenous-galactoside-binding lectins, suggested to be involved in a variety of functions, such as neurite outgrowth, synaptic connectivity, cell proliferation and apoptosis. This protein is expressed in the dorsal root ganglion (DRG) and the spinal cord in the developing and adult rats, especially intensely in small DRG neurons. In the present study, we examined whether galectin-1 is colocalized with TrkA or c-Ret mRNA in small DRG neurons and the effect of axotomy on the expression of galectin-1 in the spinal cord. About 20% of the DRG neurons showed intense galectin-1-immunoreactivity (IR). Of the intensely galectin-1-IR DRG neurons, 93.9% displayed c-Ret mRNA positive signals. On the other hand, only 6.8% displayed TrkA mRNA positive signals. Galectin-1-IR was increased in the dorsal horn at 1 to 2 weeks after axotomy. Intrathecal administration of anti-recombinant human galectin-1 antibody (anti-rhGAL-1 Ab) partially but significantly attenuated the upregulation of substance P receptor (SPR) in the spinal dorsal horn and the mechanical hypersensitivity induced by the peripheral nerve injury. These data suggest that endogenous galectin-1 may potentiate neuropathic pain after the peripheral nerve injury at least partly by increasing SPR in the dorsal horn.

Stimulation of proliferation of rat hepatic stellate cells by galectin-1 and galectin-3 through different intracellular signaling pathways

We found that the expression of galectin-1 and galectin-3 was significantly up-regulated in hepatic stellate cells (HSCs) both in the course of their transdifferentiation into myofibroblasts, a process of "self-activation," and in the fibrosis of liver tissues. Recombinant galectin-1 and galectin-3 stimulated the proliferation of cultured HSCs via the MEK1/2-ERK1/2 signaling pathway. However, galectin-3 utilized protein kinases C and A to induce this process, whereas galectin-1 did not. We also found that thiodigalactoside, a potent inhibitor of beta-galactoside binding, attenuated the effects of both galectins. In addition, galectin-1, but not galectin-3, promoted the migration of HSCs. Thus, it appears that galectin-1 and galectin-3, generated by activated HSCs, could participate in beta-galactoside binding and induce different intracellular signaling pathways leading to the proliferation of HSCs.

A proteome study of secreted prostatic factors affecting osteoblastic activity: galectin-1 is involved in differentiation of human bone marrow stromal cells

Prostate cancer cells metastasize to bone causing a predominantly osteosclerotic response. It has been shown that cells from the human prostate cancer cell line PC3 secrete factors that influence the behavior of osteoblast-like cells. Some of these factors with mitogenic activity have been found to be proteins with molecular weights between 20 and 30 kDa, but the identity of the osteoblastic mitogenic factor or factors produced by prostate cancer cells is still unknown. Therefore, the aim of this study was to characterize the protein profile of conditioned medium (CM) from PC3 cells in the molecular weight range from 5 to 30 kDa using proteome analysis. A protein profile of the CM from PC3 cells was performed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Thirty protein spots with molecular weights ranging from 5 to 30 kDa were analyzed by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). One of these spots was identified as galectin-1. We examined whether PC3 CM, recombinant galectin-1 alone, or combined with insulin-like growth factor-I (IGF-I) had any effects on the proliferation or differentiation of human bone marrow stromal (hBMS) cells. Furthermore, we tested whether adhesion of PC3 cells to plastic, laminin, fibronectin, and collagen type I was influenced by lactose, which inhibits galectin-1. Galectin-1 (1000 ng/ml) inhibited the proliferation of hBMS cells up to 70 +/- 12% (treated/control) of control in contrast to PC3 CM, which induced hBMS cell proliferation by 3-fold. This effect was abolished by IGF-I. PC3 CM and galectin-1 in concentrations of 10 and 1000 ng/ml increased the alkaline phosphatase (ALP) activity of hBMS cells up to 175 +/- 27%, 137 +/- 8%, and 131 +/- 11%, respectively, compared with ALP activity of untreated cells, and inhibited the secretion of osteocalcin (OC) up to 81 +/- 3%, 93 +/- 1%, and 58 +/- 2%, respectively, compared with OC secretion of untreated cells. These effects were affected by IGF-I. Lactose inhibited adhesion of PC3 cells to plastic, fibronectin, laminin, and collagen type I up to 58 +/- 4%, 30 +/- 12, 72 +/- 9%, and 86 +/- 4%. In conclusion, galectin-1 modulated osteoblastic proliferation and differentiation. These effects were affected by IGF-I. Thus, galectin-1 is likely be involved in the osteoblastic response, caused by prostate cancer cells metastasizing into bone, by affecting the matrix mineralization.

Galectin 1 inhibits incorporation of vitronectin and chondroitin sulfate B into the extracellular matrix of human vascular smooth muscle cells

Galectin-1, a beta-galactoside-binding dimeric lectin, interacts with the extracellular matrix (ECM) of smooth muscle cells (SMCs) and with particular ECM proteins. Enrichment of the ECM with galectin-1 affects adhesion and proliferation of cultured SMCs. Here we investigated whether galectin-1 (1) interacts with glycosaminoglycan (GAG) chains, (2) cross-links between ligands and facilitates the incorporation of GAGs, vitronectin and plasma fibronectin in the ECM of vascular SMCs. A recombinant galectin-1 fusion protein GalH, used in this study, formed dimers and interacted with ECM proteins. GAG chains inhibited these interactions. Among the studied GAG chains, only chondroitin sulfate B interacted with GalH in beta-galactoside-dependent manner. GalH did not bridge between ECM proteins on solid phase and [125I]-labelled ECM proteins or GAGs in solution. The ECM incorporated less vitronectin in the presence of soluble GalH. GalH-enriched ECM incorporated less vitronectin and chondroitin sulfate B. The ECM partially depleted of endogenous galectins incorporated more chondroitin sulfate B compared to untreated ECM. These results suggest that galectin-1 is likely to be involved in the ECM assembly affecting incorporation of some ECM components important for SMC behaviour.

Galectins-3 and -7, but not galectin-1, play a role in re-epithelialization of wounds

Disorders of wound healing characterized by impaired or delayed re-epithelialization are a serious medical problem. These conditions affect many tissues, are painful, and are difficult to treat. In this study, using cornea as a model, we demonstrate for the first time the importance of carbohydrate-binding proteins galectins-3 and -7 in re-epithelialization of wounds. In two different models of corneal wound healing, re-epithelialization of wounds was significantly slower in galectin-3-deficient (gal3(-/-)) mice compared with wild-type (gal3(+/+)) mice. In contrast, there was no difference in corneal epithelial wound closure rates between galectin-1-deficient and wild-type mice. Quantitation of the bromodeoxyuridine-labeled cells in gal3(+/+) and gal3(-/-) corneas revealed that corneal epithelial cell proliferation rate is not perturbed in gal3(-/-) corneas. Exogenous galectin-3 accelerated re-epithelialization of wounds in gal3(+/+) mice but, surprisingly, not in the gal3(-/-) mice. Gene expression analysis using cDNA microarrays revealed that healing corneas of gal3(-/-) mice contain markedly reduced levels of galectin-7 compared with those of gal3(+/+) mice. More importantly, unlike galectin-3, galectin-7 accelerated re-epithelialization of wounds in both gal3(-/-) and gal3(+/+) mice. In corresponding experiments, recombinant galectin-1 did not stimulate the corneal epithelial wound closure rate. The extent of acceleration of re-epithelialization of wounds with both galectin-3 and galectin-7 was greater than that observed in most of the published studies using growth factors. These findings have broad implications for developing novel therapeutic strategies for treating nonhealing wounds.

Galectin-1 augments Ras activation and diverts Ras signals to Raf-1 at the expense of phosphoinositide 3-kinase

Ras proteins activate diverse effector molecules. Depending on the cellular context, Ras activation may have different biological consequences: induction of cell proliferation, senescence, survival, or death. Augmentation and selective activation of particular effector molecules may underlie various Ras actions. In fact, Ras effector-loop mutants interacting with distinctive effectors provide evidence for such selectivity. Interactions of active Ras with escort proteins, such as galectin-1, could also direct Ras selectivity. Here we show that in comparison with Ras transfectants, H-Ras/galectin-1 or K-Ras4B/galectin-1 co-transfectants exhibit enhanced and prolonged epidermal growth factor (EGF)-stimulated increases in Ras-GTP, Raf-1 activity, and active extracellular signal-regulated kinase. Galectin-1 antisense RNA inhibited these EGF responses. Conversely, Ras and galectin-1 co-transfection inhibited the EGF-stimulated increase in phosphoinositide 3-kinase (PI3K) activity. Galectin-1 transfection also inhibited Ras(G12V)-induced PI3K but not Raf-1 activity. Galectin-1 co-immunoprecipitated with Ras(G12V) or with Ras(G12V/T35S) that activate Raf-1 but not with Ras(G12V/Y40C) that activates PI3K. Thus, galectin-1 binds active Ras and diverts its signal to Raf-1 at the expense of PI3K. This demonstrates a novel mechanism controlling the duration and selectivity of the Ras signal. Ras gains selectivity when it is associated with galectin-1, mimicking the selectivity of Ras(T35S), which activates Raf-1 but not PI3K.

Galectin-1 is a stromal cell ligand of the pre-B cell receptor (BCR) implicated in synapse formation between pre-B and stromal cells and in pre-BCR triggering

Although preB cell-receptor (pre-BCR) formation and cell-surface expression is essential for B cell development, pre-BCR generation of signal transduction remains elusive. Here, we report that recombinant pre-BCRs and the surrogate light chain bind specifically to the bone marrow stromal cell galectin-1 (GAL1), an S-type lectin. The surrogate light chain/GAL1 association is a direct protein-protein interaction (K(a) = 2 x 10(6) M(-1)), and the NH(2) extra loop of lambda-like is the major binding element. Pre-BCR binding to stromal cells depends upon GAL1 anchoring to glycosylated counter-receptors, and these complexes completely relocalize to form a synapse at the contact zone between preB and stromal cells. This immune developmental synapse is accompanied by the initiation of intracellular tyrosine kinase activity and signal transduction from the pre-BCR.