Inhibition by chondroitin sulfate E can specify functional Wnt/β-catenin signaling thresholds in NIH3T3 fibroblasts.
Aberrant activation of the Wnt/β-catenin signaling pathway is frequently associated with human disease, including cancer, and thus represents a key therapeutic target. However, Wnt/β-catenin signaling also plays critical roles in many aspects of normal adult tissue homeostasis. The identification of mechanisms and strategies to selectively inhibit the disease-related functions of Wnt signaling, while preserving normal physiological functions, is in its infancy. Here, we report the identification of exogenous chondroitin sulfate-E (CS-E) as an inhibitor of specific molecular and biological outcomes of Wnt3a signaling in NIH3T3 fibroblasts. We demonstrate that CS-E can decrease Wnt3a signaling through the negative regulation of LRP6 receptor activation. However, this inhibitory effect of CS-E only affected Wnt3a-mediated induction, but not repression, of target gene expression. We went on to identify a critical Wnt3a signaling threshold that differentially affects target gene induction versus repression. This signaling threshold also controlled the effects of Wnt3a on proliferation and serum starvation-induced apoptosis. Limiting Wnt3a signaling to this critical threshold, either by CS-E treatment or by ligand dilution, interfered with Wnt3a-mediated stimulation of proliferation but did not impair Wnt3a-mediated reduction of serum starvation-induced apoptosis. Treatment with pharmacological inhibitors demonstrated that both induction and repression of Wnt3a target genes in NIH3T3 cells require the canonical Wnt/β-catenin signaling cascade. Our data establish the feasibility of selective inhibition of Wnt/β-catenin transcriptional programs and biological outcomes through the exploitation of intrinsic signaling thresholds.
Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60614, USA.
Catherine M
CM
Willis
Michael
M
Klüppel
D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation / Q000187:drug effects; D002809:Chondroitin Sulfates / Q000494:pharmacology*; D015536:Down-Regulation; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D060488:Low Density Lipoprotein Receptor-Related Protein-6 / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D059467:Transcriptome; D060449:Wnt Signaling Pathway / Q000187:drug effects*; D060509:Wnt3A Protein / Q000378:metabolism*; D051176:beta Catenin / Q000037:antagonists & inhibitors / Q000378:metabolism*
D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555476:Lrp6 protein, mouse; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; D051176:beta Catenin; C038142:chondroitin sulfate glycosaminoglycan; D002809:Chondroitin Sulfates