Decoding WW domain tandem-mediated target recognitions in tissue growth and cell polarity

Abstract

WW domain tandem-containing proteins such as KIBRA, YAP, and MAGI play critical roles in cell growth and polarity via binding to and positioning target proteins in specific subcellular regions. An immense disparity exists between promiscuity of WW domain-mediated target bindings and specific roles of WW domain proteins in cell growth regulation. Here, we discovered that WW domain tandems of KIBRA and MAGI, but not YAP, bind to specific target proteins with extremely high affinity and exquisite sequence specificity. Via systematic structural biology and biochemistry approaches, we decoded the target binding rules of WW domain tandems from cell growth regulatory proteins and uncovered a list of previously unknown WW tandem binding proteins including β-Dystroglycan, JCAD, and PTPN21. The WW tandem-mediated target recognition mechanisms elucidated here can guide functional studies of WW domain proteins in cell growth and polarity as well as in other cellular processes including neuronal synaptic signaling.

Profiling of the muscle-specific dystroglycan interactome reveals the role of Hippo signaling in muscular dystrophy and age-dependent muscle atrophy

“…In accordance with the studies in mammalian heart muscles [36,78], our current work also demonstrates that in Drosophila muscles, Dg associates with Yki, suggesting that the previously proposed Dg function in Yki/ Yap sequestration could be conserved. In addition, our data show that in Drosophila, Dg interacts with another Hippo pathway factor, Kbr, and recent studies demonstrated the possibility of Kbr-Dg interaction in human cells [74]. Therefore, we tested if Dg interacts with Kbr in mammalian muscles.…”

“…We specifically focused on Dg interaction with a critical component of this mechanotransducing pathway, Kbr. While binding of Dg peptide to Kbr WW tandem has been recently reported [74], Dg-Kbr interaction has not been demonstrated in any animal in vivo. We expressed a GFP-tagged Dg protein using Mhc-Gal4 and immunoprecipitated complexes from whole fly extracts using anti-GFP beads.…”

“…In addition, Drosophila Yki also contains WW domains (Additional file 2: Figure S4), and Dg-Yap binding through PPxY-WW interaction has been recently demonstrated in mice [36]. However, a recent study showed that in human cells, Dg can bind the WW tandem domain of Kbr, but not Yki/Yap [74]. Therefore, further studies are required to further dissect the biochemistry of Dg interaction with these Hippo signaling factors.…”

“…It has also been previously established that Dg contains two conserved PPxY motifs at the C-terminal end; both of them are functional and can mediate interaction with Dys protein in mammals and flies [13,19,71,72]. Intriguingly, it has been recently demonstrated that the WW domain of Kbr, but not YAP, can bind the beta-Dg peptide [74]; therefore, further in vivo studies are necessary to clarify the mode of Dg interaction with these two Hippo signaling components.…”

A WW Tandem-Mediated Dimerization Mode of SAV1 Essential for Hippo Signaling

“…Recently, we demonstrated that the WW-domain-containing proteins (e.g., KIBRA, YAP, MAGI2, and MAGI3) involved in cell growth and polarity use their WW tandems to bind to specific targets containing multiple PY motifs. Such WW-tandem-mediated target interactions allow formation of very stable and highly specific WW domain protein/target complexes required for cell growth and signaling ( Ji et al, 2019 ; Lin et al, 2019 ). The WW-tandem-mediated target recognition has also been reported in other multiple WW domain proteins, such as HECT family E3 ubiquitin ligases ( Chong et al, 2010 ).…”