Two distantly positioned PDZ domains mediate multivalent INAD-phospholipase C interactions essential for G protein-coupled signaling

• Published in: The EMBO journal Vol. 17; no. 8; pp. 2285 - 2297
• Main Authors: Huizen, R. van, Miller, K, Chen, D.M, Li, Y, Lai, Z.C, Raab, R.W, Stark, W.S, Shortride, R.D, Li, M
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 15-04-1998
• Subjects: Amino Acid Sequence; amino acid sequences; Animals; Animals, Genetically Modified; binding; binding proteins; Binding Sites; compound eyes; deletions; Drosophila melanogaster; Drosophila melanogaster - metabolism; Drosophila melanogaster - physiology; Drosophila Proteins; electrophysiology; electroretinography; Eye Proteins - genetics; Eye Proteins - metabolism; G protein; GTP-Binding Proteins - metabolism; guanosine triphosphate; INAD; Isoenzymes - genetics; Isoenzymes - metabolism; Molecular Sequence Data; Mutagenesis; ommatidia; PDZ; phospholipase C; Phospholipase C beta; Photoreceptor Cells, Invertebrate - metabolism; PLC; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sequence Homology, Amino Acid; Type C Phospholipases - genetics; Type C Phospholipases - metabolism; Vision, Ocular - physiology
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/17.8.2285

Drosophila INAD, which contains five tandem protein interaction PDZ domains, plays an important role in the G protein‐coupled visual signal transduction. Mutations in InaD alleles display mislocalization of signaling molecules of phototransduction which include the essential effector, phospholipase C‐β (PLC‐β), which is also known as NORPA. The molecular and biochemical details of this functional link are unknown. We report that INAD directly binds to NORPA via two terminally positioned PDZ1 and PDZ5 domains. PDZ1 binds to the C‐terminus of NORPA, while PDZ5 binds to an internal region overlapping with the G box‐homology region (a putative G protein‐interacting site). The NORPA proteins lacking binding sites, which display normal basal PLC activity, can no longer associate with INAD in vivo. These truncations cause significant reduction of NORPA protein expression in rhabdomeres and severe defects in phototransduction. Thus, the two terminal PDZ domains of INAD, through intermolecular and/or intramolecular interactions, are brought into proximity in vivo. Such domain organization allows for the multivalent INAD–NORPA interactions which are essential for G protein‐coupled phototransduction.