galectin

Galectins are a family of beta-galactoside-binding proteins known as lectins. They are defined by a conserved carbohydrate-recognition domain that binds beta-galactosides, and they generally lack a classical signal peptide, allowing diverse cellular localization. The human genome encodes several galectins, categorized by structural organization into prototype (for example galectin-1 and galectin-2), chimera-type (galectin-3), and tandem-repeat types (galectins-4, -8, -9, -12).

Galectins participate in cell–cell and cell–matrix interactions by crosslinking glycoproteins on the surface of cells and the extracellular matrix. They regulate immune responses by modulating leukocyte activation, cytokine production, and apoptosis, and they influence processes such as angiogenesis, fibrosis, and tumor progression. Certain galectins have context-dependent effects: for example, galectin-3 can promote cell survival and metastasis, while galectin-9 can interact with Tim-3 to modulate T cell activity.

Localization and secretion: many galectins are found intracellularly, while others are secreted by non-classical pathways and function in the extracellular space where they organize glycoprotein lattices to influence receptor signaling.

Clinical relevance: altered galectin expression has been associated with cancer, autoimmune disease, fibrosis, and infectious disease. Galectins are explored as biomarkers and as therapeutic targets; several galectin inhibitors and agents modulating galectin interactions have entered research and development and early clinical testing.