Induction of Terminal Differentiation in Epithelial Cells Requires Polymerization of Hensin by Galectin 3

Abstract

During terminal differentiation, epithelia become columnar and develop specialized apical membrane structures (microvilli) and functions (regulated endocytosis and exocytosis). Using a clonal intercalated epithelial cell line, we found that high seeding density induced these characteristics, whereas low density seeding maintained a protoepithelial state. When cells were plated at low density, but on the extracellular matrix of high density cells, they converted to the more differentiated phenotype. The extracellular matrix (ECM) protein responsible for this activity was purified and found to be a large 230-kD protein, which we termed hensin. High density seeding caused hensin to be polymerized and deposited in the extracellular matrix, and only this form of hensin was able to induce terminal differentiation. Antibodies to hensin blocked the change in phenotype. However, its purification to homogeneity resulted in loss of activity, suggesting that an additional protein might be necessary for induction of terminal differentiation. Here, we found that a 29-kD protein specifically associates with hensin in the ECM. Addition of purified p29 restored the activity of homogenously purified hensin. Mass fingerprinting identified p29 as galectin 3. Purified recombinant galectin 3 was able to bind to hensin and to polymerize it in vitro. Seeding cells at high density induced secretion of galectin 3 into the ECM where it bundled hensin. Hence, the high density state causes a secretion of a protein that acts on another ECM protein to allow the new complex to signal the cell to change its phenotype. This is a new mechanism of inside-out signaling.

Galectin-12 Is Required for Adipogenic Signaling and Adipocyte Differentiation

“…In mammals, 14 members have been identified to date (16). Some of the members, especially galectin-3 and galectin-1, have been extensively studied, and experimental results suggest that these lectins may have diverse functions, including regulation of pre-mRNA splicing, cell proliferation and differentiation, and apoptosis (17)(18)(19)(20)(21)(22)(23). Most galectins have wide tissue distribution.…”

Ly6 family member C4.4A binds laminins 1 and 5, associates with galectin‐3 and supports cell migration

“…8,52,53 C4.4A associates with galectin-3, which was shown using the purified recombinant C4.4A protein as well the native C4.4A protein. Because C4.4A binding was lost in the presence of 100 mM lactose, the interaction between C4.4A and galectin-3 likely depends on the lectin domain.…”

Differentiation of columnar epithelia: the hensin pathway

“…It can convert hensin monomers to dimers. Moreover, extraction of galectin 3 from insoluble hensin removes its ability to convert cells to columnar epithelia and adding galectin3 back restores this ability (Hikita et al, 2000). This suggests that galectin 3 not only stimulates formation of the hensin fibril, perhaps by making hensin dimers, but also might maintain these multimers in the correct orientation.…”