Newton, I. P. | Search bioRxiv

bioRxiv2018

Identification of endogenous Adenomatous polyposis coli interaction partners and β-catenin-independent targets by proteomics

Adenomatous polyposis coli (APC) is the most frequently mutated gene in colorectal cancer. APC negatively regulates the pro-proliferative Wnt signaling pathway by promoting the degradation of {beta}-catenin, but the extent to which APC exerts Wnt/{beta}-catenin-independent tumor suppressive activity is unclear. To identify interaction partners and {beta}-catenin-independent targets of endogenous, full-length APC, we applied label-free and multiplexed TMT mass spectrometry. Affinity enrichment-mass spectrometry revealed over 150 previously unidentified APC interaction partners. Moreover, our global proteomic analysis revealed that roughly half of the protein expression changes that occur in response to APC loss are independent of {beta}-catenin. By combining these two analyses, we identified Misshapen-like kinase 1 (MINK1) as a putative substrate of an alternative APC-containing destruction complex and provide evidence for the potential contribution of MINK1 to APC mutant phenotypes. Collectively, our results highlight the extent and importance of Wnt-independent APC functions in epithelial biology and disease.

cancer biology↗

bioRxiv2017

Postmitotic Separation Enables Selective Niche Retention Of One Daughter Cell In Intestinal Crypts And Is Facilitated By Interkinetic Nuclear Migration And Basal Tethering

Homeostasis of renewing tissues requires balanced proliferation, differentiation and movement. This is particullary important in the intestinal epithelium where lineage tracing suggests that stochastic differentiation choices are intricately coupled to position. To determine how position is achieved we followed proliferating cells in intestinal organoids and discovered that behaviour of mitotic sisters predicted long-term positioning. Normally, 70% of sisters remain neighbours while 30% lose contact separating after cytokinesis. Postmitotic placements predict differences in positions of sisters later: adjacent sisters reach similar positions; one separating sister remains close to its birthplace, the other moves upward. Computationally modelling crypt dynamics confirmed post-mitotic separation as a mechanism for placement of sisters into different niches. Separation depends on interkinetic nuclear migration, cell size, and asymmetric tethering by a basal process. These processes are altered when Adenomatous polyposis coli (Apc) is mutant and separation is lost. We conclude that post-mitotic placement enables stochastic niche exit and when defective, supports the clonal expansion of Apc mutant cells.

cancer biology↗