Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2022.09.25.509379

EGFR-initiated endocytosis of Wnt9a and Fzd9b is required for β-catenin signaling

Nguyen, N.·Carpenter, K. A.·Thurlow, K. E.·Mu, E. M.·Gilliland, C.·Grainger, S.
View original source ↗Export metadata ↓

Abstract

Cell to cell communication through secreted ligands like those encoded by the Wnt gene family is critical for development and homeostasis during organismal life. One of the bottlenecks in the Wnt field has been identifying specific ligand/receptor pairings and decoding the mechanisms for their downstream signals. We previously discovered that the Wnt9a ligand signals through the cell surface receptors Fzd9b, LRP5/6 and EGFR to promote early proliferation of hematopoietic stem cells during development. We used this exquisitely specific ligand/receptor complex as a platform to determine if Wnt9a requires endocytosis for signaling. Using fluorescently labeled, biologically active Wnt9a and Fzd9b fusion proteins, we demonstrate here that the Wnt9a receptor complex is rapidly endocytosed within one minute of contact with Fzd9b. Following this, the Wnt9a/Fzd9b complex is trafficked through the cell to early and late endosomes, lysosomes, and the endoplasmic reticulum; it is also recycled back to the membrane. Using small molecule inhibitors, genetic and siRNA approaches, we identified that mechanistically this endocytosis requires EGFR-mediated phosphorylation of the Fzd9b tail, followed by endocytosis through a caveolin and EPS15 dependent pathway. Specific modes of endocytosis and trafficking may represent one of the ways in which Wnt/Fzd specificity is established, since other Wnt ligands do not require endocytosis for activity.

Source connections

Explore related subjects

cell biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Nguyen, N., Carpenter, K. A., Thurlow, K. E., Mu, E. M., Gilliland, C., Grainger, S.. 2022-09-26. EGFR-initiated endocytosis of Wnt9a and Fzd9b is required for β-catenin signaling. https://doi.org/10.1101/2022.09.25.509379

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Unraveling the metabolic landscape of alkaptonuria through a human-relevant in vitro liver disease model

Alkaptonuria (AKU) is a rare inherited metabolic disorder of tyrosine catabolism caused by a deficient homogentisate 1,2-dioxygenase (HGD) enzyme. This results in the accumulation of homogentisic acid (HGA), driving a progressive multisystem pathology characterized by debilitating early-onset osteoarthritis due to connective tissue degeneration. While previous in vitro studies have primarily relied on exogenous HGA exposure in osteoarticular cell models, the direct metabolic consequences of endogenous HGD deficiency within its native hepatic context remain poorly understood. Here, we established the first human-relevant HGD knockout hepatic in vitro model using a universal in-house-developed homology-directed repair approach. Integrative multi-omic analysis revealed that HGD deficiency induces widespread metabolic rewiring extending beyond disrupted tyrosine catabolism. HGD-deficient hepatocytes exhibited elevated oxidative stress accompanied by impaired mitochondrial respiration and a pseudohypoxic metabolic adaptation toward increased glycolytic dependency. Despite this glycolytic shift, the cells displayed reduced anabolic and translational activity alongside attenuated proliferation, consistent with a chronic stress-adaptive survival state rather than a proliferative metabolic phenotype. This study provides systems-level insights into the pathophysiology of AKU and establishes a versatile platform for mechanistic and therapeutic investigation.

cell biology↗
bioRxiv2026

P-body sequestration of clock transcripts delays repressor synthesis to set circadian period in Drosophila

Negative-feedback oscillators require a delay between the accumulation of a repressor's mRNA and the action of its protein. In the circadian clock, this delay has been attributed largely to post-translational control of PERIOD (PER) stability and nuclear entry. The RNA-binding proteins shown to regulate per translation, ATAXIN2 and its partners, promote it, leaving open whether any step holds clock transcripts back before they are translated. Here, using time-resolved miniTurbo proximity labeling of endogenous PER across four phases of the circadian cycle in Drosophila clock neurons, we define a 252-protein PER proximitome that partitions into a nuclear arm and a cytoplasmic RNA-metabolism arm. A behavioral RNAi screen identified two P-body components, the DEAD-box helicase Me31B (DDX6) and the 5'-3' exonuclease Pacman (Pcm; XRN1), as strong regulators of circadian rhythms. Using single-molecule RNA-FISH, proximity RNA editing and ribosome profiling, we show that as per and tim transcripts accumulate, they localize to Me31B-labeled P-bodies and are poorly translated, most prominently at ZT12. Me31B knockdown disrupts P-bodies and releases per mRNA from them, causing PER to accumulate earlier and to ~2-fold higher levels, whereas Me31B overexpression delays PER accumulation and lengthens the free-running period by ~2 h. Knockdown of Pcm, in contrast, impairs clearance of per mRNA, sustaining PER and TIM accumulation, prolonging the repression phase and abolishing cycling of ~89% of rhythmic transcripts. Together, these findings identify P-body sequestration as a repressive step that delays repressor synthesis, and Pcm-dependent decay as required to end repression on time. Given the deep conservation of DDX6 and XRN1, RNP compartments may provide a conserved means of generating delay in circadian and other negative-feedback circuits.

cell biology↗
bioRxiv2026

Defining redundancy in the stickers and spacers of the cell-cell junction protein Canoe's intrinsically disordered region

Cell-cell adherens junctions (AJs) and their dynamic cytoskeletal linkage power morphogenesis. AJs are enormous complexes with hundreds of proteins linked by multivalent interactions. Like other biomolecular condensates, intrinsically disordered regions (IDRs) in junctional proteins play important roles in AJ assembly and function, using spacer elements to span distances, and stickers to engage targets. To define molecular mechanisms, we need to define the functional units within IDRs. Drosophila Canoe, homolog of human Afadin, is our model. Canoe mediates morphogenesis and has an extensive IDR, with two conserved F-actin-binding stickers and two poorly conserved spacers. We combined biochemical, genetic and cell biological approaches to define the function of these IDR elements. While no single element is essential, deleting the full IDR essentially eliminates Canoe function. By scrambling the amino acid sequence of the spacers, we find that length and composition are more important than amino acid sequences, though sequences in the C-terminal spacer affect Canoe localization. Finally, we test redundancy of the F-actin-binding stickers. Deleting both reduces but does not eliminate viability, and sensitized assays reveal their redundant roles. These data reveal the robustness of IDRs.

cell biology↗