Drosophila melanogaster Guk-holder interacts with the Scribbled PDZ1 domain and regulates epithelial development with Scribbled and Discs Large

Abstract

Epithelial cell polarity is controlled by components of the Scribble polarity module, and its regulation is critical for tissue architecture and cell proliferation and cell migration. In Drosophila melanogaster, the adaptor protein Guk-holder (Gukh) binds to the Scribbled (Scrib) and Discs Large (Dlg) components of the Scribble polarity module and plays an important role in the formation of neuromuscular junctions. However, Gukh's role in epithelial tissue formation and the molecular basis for the Scrib-Gukh interaction remain to be defined. We now show using isothermal titration calorimetry that the Scrib PDZ1 domain is the major site for an interaction with Gukh. Furthermore, we defined the structural basis of this interaction by determining the crystal structure of the Scrib PDZ1-Gukh complex. The C-terminal PDZ-binding motif of Gukh is located in the canonical ligand binding groove of Scrib PDZ1, and utilizes an unusually extensive network of hydrogen bonds and ionic interactions to enable binding to PDZ1 with high affinity. We next examined the role of Gukh along with those of Scrib and Dlg in Drosophila epithelial tissues, and found that Gukh is expressed in larval-wing and eye-epithelial tissues and co-localizes with Scrib and Dlg at the apical cell cortex. Importantly, we show that Gukh functions with Scrib and Dlg in the development of Drosophila epithelial http://www.jbc.org/cgi

Crystal structure of the human Scribble PDZ1 domain bound to the PDZ‐binding motif of APC

“…3B). This suggests that to achieve similar affinities, interactions by hydrophobic PBM resides at the À4, À5 or À6 position such as those observed in the Gukh [28], ZO1 [42] or a high affinity artificial peptide [43] complexes are not required. Similarly, the high affinity interaction of APC with the DLG1 PDZ2 domain does not involve specific engagement of the b2-3 loop by Tyr at the À5 position in the APC PBM (Fig.…”

Lgl cortical dynamics are independent of binding to the Scrib-Dlg complex but require Dlg-dependent restriction of aPKC

“…To identify how Dlg binds Scrib, we induced clustering of Scrib versions lacking major protein interacting domains, namely the leucine-rich repeats (DLRR-GFP) or the PDZ domains (DPDZ-GFP), which bind the Dlg binding protein GUK-holder (Caria et al, 2018), and were recently shown to play specific roles in the establishment of polarity, tricellular junction formation and mitotic spindle orientation in Drosophila (Bonello et al, 2019;Sharifkhodaei et al, 2019;Nakajima et al, 2019). Both proteins display largely cytoplasmic localization ( Figure 4D), but removal of the PDZ domains still enables cortical enrichment as previously reported (Albertson et al, 2004;Zeitler et al, 2004).…”

SGEF forms a complex with Scribble and Dlg1 and regulates epithelial junctions and contractility

“…In Drosophila , a protein called GUK-holder (GUKH) also forms a ternary complex with Dlg1 and Scribble ( Mathew et al, 2002 ). Like SGEF, GUKH binds to the GUK domain of Dlg1 and to PDZ1 in Scribble, although through a C-terminal PBM ( Mathew et al, 2002 ; Caria et al, 2018 ). In contrast to SGEF, GUKH functions exclusively as a scaffold and has no known enzymatic activity.…”