title: Heterotrimeric Gα subunit from wheat (Triticum aestivum), GA3, interacts with the calcium-binding protein, Clo3, and the phosphoinositide-specific phospholipase C, PI-PLC1.
abstract: The canonical Gα subunit of the heterotrimeric G protein complex from wheat (Triticum aestivum), GA3, and the calcium-binding protein, Clo3, were revealed to interact both in vivo and in vitro and Clo3 was shown to enhance the GTPase activity of GA3. Clo3 is a member of the caleosin gene family in wheat with a single EF-hand domain and is induced during cold acclimation. Bimolecular Fluorescent Complementation (BiFC) was used to localize the interaction between Clo3 and GA3 to the plasma membrane (PM). Even though heterotrimeric G-protein signaling and Ca²⁺ signaling have both been shown to play a role in the response to environmental stresses in plants, little is known about the interaction between calcium-binding proteins and Gα. The GAP activity of Clo3 towards GA3 suggests it may play a role in the inactivation of GA3 as part of the stress response in plants. GA3 was also shown to interact with the phosphoinositide-specific phospholipase C, PI-PLC1, not only in the PM but also in the endoplasmic reticulum (ER). Surprisingly, Clo3 was also shown to interact with PI-PLC1 in the PM and ER. In vitro analysis of the protein-protein interaction showed that the interaction of Clo3 with GA3 and PI-PLC1 is enhanced by high Ca²⁺ levels. Three-way affinity characterizations with GA3, Clo3 and PI-PLC1 showed the interaction with Clo3 to be competitive, which suggests that Clo3 may play a role in the Ca²⁺-triggered feedback regulation of both GA3 and PI-PLC1. This hypothesis was further supported by the demonstration that Clo3 has GAP activity with GA3.
authors: Department of Biology, Concordia University, 7141 Sherbrooke W., Montreal, QC H4B1R6, Canada.
authors: Hala Badr
authors: HB
authors: Khalil
authors: Zhejun
authors: Z
authors: Wang
authors: Justin A
authors: JA
authors: Wright
authors: Alexandra
authors: A
authors: Ralevski
authors: Ariel O
authors: AO
authors: Donayo
authors: Patrick J
authors: PJ
authors: Gulick
mesh_terms: D000595:Amino Acid Sequence; D001667:Binding, Competitive; D002135:Calcium-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D054801:Phosphoinositide Phospholipase C / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism* / Q000502:physiology; D016415:Sequence Alignment; D015398:Signal Transduction; D013379:Substrate Specificity; D014908:Triticum / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D044385:GTP-Binding Protein alpha Subunits; D010940:Plant Proteins; D054801:Phosphoinositide Phospholipase C