Phosphatidic acid binds to and inhibits the activity of Arabidopsis CTR1. J Exp Bot

Section of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 318, NL-1098 SM Amsterdam, The Netherlands.
Journal of Experimental Botany (Impact Factor: 5.53). 02/2007; 58(14):3905-14. DOI: 10.1093/jxb/erm243
Source: PubMed


Phosphatidic acid (PA) has only recently been identified as an important eukaryotic lipid-signalling molecule. In plants,
PA formation is triggered by various biotic and abiotic stresses, including wounding, pathogen attack, drought, salinity,
cold, and freezing. However, few molecular targets of PA have been identified so far. One of the best characterized is Raf-1,
a mammalian MAPKKK. Arabidopsis thaliana CTR1 (constitutive triple response 1) is one of the plant homologues of Raf-1 and functions as a negative regulator of the
ethylene signalling pathway. Here, it is shown that PA binds CTR1 and inhibits its kinase activity. Using different PA-binding
assays, the kinase domain of CTR1 (CTR1-K) was found to bind PA directly. Addition of PA resulted in almost complete inhibition
of CTR1 kinase activity and disrupted the intramolecular interaction between CTR1-K and the CTR1 N-terminal regulatory domain.
Additionally, PA blocked the interaction of CTR1 with ETR1, one of the ethylene receptors. The basic amino acid motif shown
to be required for PA binding in Raf-1 is conserved in CTR1-K. However, mutations in this motif did not affect either PA-binding
or PA-dependent inhibition of CTR1 activity. Subsequent deletion analysis of CTR1’s kinase domain revealed a novel PA-binding
region at the C-terminus of the kinase.

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Available from: Teun Munnik, Jun 04, 2014
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    • "PA is also able to bind to CTR1 kinase in A. thaliana, resulting in inhibition of its activity. This process could contribute to the activation of ethylene signalling pathway in the absence of ethylene itself (Testerink et al., 2007). Although, provided that CTR1 is colocalised with ethylene receptor at the ER, an allocation of different pool of PA (comparing to plasma membrane PA) to this process should be considered. "
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    • "Arabidopsis SnRK2.4 is rapidly and transiently activated in saline conditions and is targeted to punctate structures in epidermal and cortex cells in roots (McLoughlin et al., 2012). Activity of class 1 SnRK2 kinases is not directly regulated by PA (Testerink et al., 2007), therefore PA might spatially facilitate protein–protein interactions. Several proteins that interact or are regulated by class 1 SnRK2 kinases also bind to PA (Figure 1B). "
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