title: Galectin-3 mediates oligomerization of secreted hensin using its carbohydrate-recognition domain.
abstract: A multidomain, multifunctional 230-kDa extracellular matrix (ECM) protein, hensin, regulates the adaptation of rabbit kidney to metabolic acidosis by remodeling collecting duct intercalated cells. Conditional deletion of hensin in intercalated cells of the mouse kidney leads to distal renal tubular acidosis and to a significant reduction in the number of cells expressing the basolateral chloride-bicarbonate exchanger kAE1, a characteristic marker of α-intercalated cells. Although hensin is secreted as a monomer, its polymerization and ECM assembly are essential for its role in the adaptation of the kidney to metabolic acidosis. Galectin-3, a unique lectin with specific affinity for β-galactoside glycoconjugates, directly interacts with hensin. Acidotic rabbits had a significant increase in the number of cells expressing galectin-3 in the collecting duct and exhibited colocalization of galectin-3 with hensin in the ECM of microdissected tubules. In this study, we confirmed the increased expression of galectin-3 in acidotic rabbit kidneys by real-time RT-PCR. Galectin-3 interacted with hensin in vitro via its carbohydrate-binding COOH-terminal domain, and the interaction was competitively inhibited by lactose, removal of the COOH-terminal domain of galectin-3, and deglycosylation of hensin. Galectin-9, a lectin with two carbohydrate-recognition domains, is also present in the rabbit kidney; galectin-9 partially oligomerized hensin in vitro. Our results demonstrate that galectin-3 plays a critical role in hensin ECM assembly by oligomerizing secreted monomeric hensin. Both the NH₂-terminal and COOH-terminal domains are required for this function. We suggest that in the case of galectin-3-null mice galectin-9 may partially substitute for the function of galectin-3.
authors: Department of Pediatrics (Pediatric Nephrology), University of Rochester School of Medicine, Rochester, NY, USA.
authors: Soundarapandian
authors: S
authors: Vijayakumar
authors: Hu
authors: H
authors: Peng
authors: George J
authors: GJ
authors: Schwartz
mesh_terms: D000138:Acidosis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D004195:Disease Models, Animal; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005260:Female; D037502:Galectin 3 / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D007668:Kidney / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D011817:Rabbits; D060888:Real-Time Polymerase Chain Reaction; D051116:Receptors, Scavenger / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
chemical_list: D016326:Extracellular Matrix Proteins; D037502:Galectin 3; D051116:Receptors, Scavenger; D011994:Recombinant Proteins; C495130:hensin protein, rabbit; D007785:Lactose
keywords: clone C; collecting duct; extracellular matrix; intercalated cell; metabolic acidosis
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