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

Abstract

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.

Increased protein kinase Cδ in mammary tumor cells: relationship to transformation and metastatic progression

“…Although our studies focused on STICKs, several other categories of PKC binding proteins, some of which are isozyme selective, have been identi®ed. These potential targeting proteins include RACKs, PICKs, PH domain proteins, InaD and others (reviewed in Jaken, 1997;Mochly-Rosen and Gordon, 1998) (see also Wu et al, 1998;Van Huizen et al, 1998;Yao et al, 1994). Regardless of the mechanism, our studies provide convincing evidence that RDd selectively interferes with signaling through PKCd pathways.…”

M3 Muscarinic Receptor Interaction with Phospholipase C β3 Determines Its Signaling Efficiency

“…PDZ domains are independently folded protein modules that specifically bind and recognize PDZ ligand consensus sequences at the extreme C terminus of target proteins (21,22). PDZ domain-containing proteins generally have multiple individual PDZ domains and thus can scaffold target proteins together (21)(22)(23). All PLC␤ isoforms have PDZ ligand motifs at their C terminus with a consensus sequence (X(S/T)X(V/L)-COOH) (21,22).…”

Molecular genetics of retinal degeneration: A Drosophila perspective

“…Moreover, several signaling proteins including TRP, NORPA and eye-PKC (eye-specific protein kinase C) are organized into a macromolecular signaling complex (transduciosome or signalplex) ( fig. 2) through the association with INAD (inactivation-noafterpotential D), [34][35][36][37][38][39] a multivalent scaffolding protein containing five PDZ domains. INAD is critical for the subcellular localization as well as the stability of its interacting proteins in vivo, and it promotes fast activation and deactivation of the visual response.…”