Systematic mapping of WNT-Frizzled interactions reveals functional selectivity by distinct WNT-Frizzled pairs

• Authors: JACOMIJN P. Dijksterhuis; BALJINNYAM Bolormaa; STANGER Karen; O SERCAN Hakki; JI Yun; ANDRES Osler; RUBIN Jeffrey S.; HANNOUSH Rami N.; SCHULTE Gunnar
• Year of publication: 2015
• Type: Article in Periodical
• Magazine / Source: The Journal of Biological Chemistry
• MU Faculty or unit: Faculty of Science
• Doi: http://dx.doi.org/10.1074/jbc.M114.612648
• Field: Physiology
• Keywords: WNT pathway; WNT signaling; beta catenin (B catenin); disheveled; LDL receptor-related protein 6 (LRP6); myeloid cell; receptor; 32D cells; Frizzled; functional selectivity
• Description: The seven transmembrane spanning receptors of the Class Frizzled (FZD1-10) are bound and activated by the WNT family of lipoglycoproteins, thereby inducing a complex network of signaling pathways. Yet the specificity of interaction between mammalian WNT and FZD proteins and the subsequent signaling cascade downstream of the different WNT FZD pairs has not been systematically addressed to date. In this report, we determine the binding affinities of various WNT proteins to different members of the FZD family by using biolayer interferometry and characterize their functional selectivity in a cellular system. Using purified WNT proteins, we show that different FZD cysteine rich domains (CRD) prefer to bind to distinct WNTs with fast onrates and slow off-rates. In a 32D cell-based system engineered to overexpress FZD(2), FZD(4), or FZD(5), we found that WNT-3A (but not WNT-4, -5A, or -9B) activated the WNT-beta-catenin pathway through FZD(2/4/5) as measured by phosphorylation of LRP6 and beta-catenin stabilization. Surprisingly, different WNT-FZD pairs showed differential effects on phosphorylation of DVL2 and DVL3, revealing a previously unappreciated DVL isoform selectivity by different WNT-FZD pairs in 32D cells. In summary, we present extensive mapping of WNT-FZD cysteine-rich domain interactions complemented by analysis of WNT-FZD pair functionality in a unique cell system expressing individual FZD isoforms. Differential WNT-FZD binding and selective functional readouts suggest that endogenous WNT ligands evolved with an intrinsic natural bias toward different downstream signaling pathways, a phenomenon that could be of great importance in the design of FZD-targeting drugs.