Galectin-3 in the Regulation of Apoptosis Induced by Loss of Cell-Matrix Interactions.

摘要

Galectin-3 is a multifunctional oncogenic protein found in the nucleus, cytoplasm and also extracellular milieu. Although recent studies demonstrated an anti-apoptotic activity of galectin- 3, neither the functional site nor the mechanism of how galectin-3 regulates apoptosis is known. During the funding period, we examined the subcellular localization of galectin-3 during apoptosis and investigated its anti-apoptotic actions. Confocal microscopy and biochemical analysis revealed that galectin-3 is enriched in the mitochondria and prevents mitochondrial damage and cytochrome c release. Using a yeast two-hybrid system we screened for galectin-3 interacting proteins that regulate galectin-3 localization and anti-apoptotic activity. Synexin, a Ca2+- and phospholipid binding protein, was one of the proteins identified. We confirmed direct interaction between galectin-3 and synexin by GST-pulldown assay in vitro. We showed that galectin-3 fails to translocate to the perinuclear membranes when the expression of synexin is downregulated using an Oligodeoxyribonucleotide complementary to the synexin mRNA, suggesting a role for synexin in galectin-3 trafficking. Furthermore, synexin downregulation abolished anti-apoptotic activity of galectin-3. Taken together, our study suggests that synexin mediates galectin-3 translocation to the perinuclear mitochondrial membranes, where it regulates mitochondrial integrity critical for apoptosis regulation.