Biology subjects

Wunder, C.

Publications and source records attributed to Wunder, C..

3 recordsLinked to original sources

bioRxiv2025

Galectin-3 Mediated Endocytosis of the Orphan G-Protein-Coupled Receptor GPRC5A

Galectins, a family of glycan-binding proteins, play crucial roles in various cellular functions, acting at both intracellular and extracellular levels. Among them, Galectin-3 (Gal-3) stands out as a unique member, possessing an intrinsically disordered N-terminal interaction domain and a canonical carbohydrate-recognition domain (CRD). Gal-3 binding to glycosylated plasma membrane cargo leads to its oligomerization and membrane bending, ultimately resulting in the formation of endocytic invaginations. An interactomic assay using proteomic analysis of endogenous Gal-3 immunoprecipitates identified the orphan G protein-coupled receptor GPRC5A as a novel binding partner of Gal-3. GPRC5A, also known as Retinoic Acid-Induced protein 3 (RAI3), is transcriptionally induced by retinoic acid. Our results further demonstrate that extracellular recombinant Gal-3 stimulates GPRC5A internalization. In SW480 colorectal cancer cells, glycosylated GPRC5A interacts with Gal-3. Interestingly, while GPRC5A expression was upregulated by the addition of all-trans retinoic acid (ATRA), its endogenous internalization in SW480 cells was specifically triggered by extracellular Gal-3, but not by ATRA. This study provides new insights into the endocytic mechanisms of GPRC5A, for which no specific ligand has been identified to date. Further research may uncover additional Gal-3 mediated functions in GPRC5A cellular signaling and contribute to the development of innovative therapeutic strategies.

cell biology↗

bioRxiv2023

Spatial N-glycan rearrangement on α5β1 integrin nucleates galectin-3 oligomers to determine endocytic fate α

Membrane glycoproteins frequently adopt different conformations when altering between active and inactive states. Here, we discover a molecular switch that exploits dynamic spatial rearrangements of N-glycans during such conformational transitions to control protein function. For the conformationally switchable cell adhesion glycoprotein 5{beta}1 integrin, we find that only the bent-closed state arranges N-glycans to nucleate the formation of up to tetrameric oligomers of the glycan-binding protein galectin-3. We propose a structural model of how these galectin-3 oligomers are assembled and how they clamp the bent-closed state to prime it for endocytic uptake and subsequent retrograde trafficking to the Golgi for polarized distribution in cells. Our findings highlight an unexpectedly dynamic regulation of the glycan landscape at the cell surface to achieve oligomerization of galectin-3. Galectin-3 oligomers are thereby identified as decoders of defined spatial patterns of N-glycans and as functional extracellular interactors of specifically the bent- closed conformational state of 5{beta}1 integrin and possibly other family members.

cell biology↗

bioRxiv2023

Growth factor-induced desialylation for the fast control of endocytosis

It is commonly assumed that the glycan makeup of glycoproteins that reach the cell surface is final and static. Here, we challenge this notion by the discovery of a molecular switch that induces acute and reversible changes of glycans on the plasma membrane. We demonstrate that within minutes, the epidermal growth factor triggers the galectin-driven endocytosis of cell surface glycoproteins, such as integrins, that are key regulators of cell adhesion and migration. The onset of this process, mediated by the Na+/H+ antiporter NHE-1 and the neuraminidases Neu1/3, requires the pH-triggered enzymatic removal of sialic acids whose presence otherwise prevents galectin binding. Desialylated glycoproteins are then retrogradely transported to the Golgi apparatus where their glycan makeup is reset, and their function is repurposed to regulate EGF-dependent invasive cell migration. Glycosylation at the cell surface thereby emerges as a dynamic and reversible regulatory post-translational modification that controls a highly adaptable trafficking pathway.

cell biology↗