Phospholipase A₂ affects the activity of fusicoccin receptors

Abstract

Biochemical properties of fusicoccin receptors are strongly influenced by the phospholipid environment. In this report we have studied the effect of different exogenous phospholipases on fusicoccin binding ability of both plasma membrane and solubilised receptors. Among the phospholipases tested only phospholipase A, showed an inhibitory effect on fusicoccin binding. In particular, the influence of this enzyme on the time course and reversibility of the fusicoccin binding reaction was studied. The inhibitory effect of phospholipase A, was the consequence of fatty acid release. The usual fatty acids of plasma membrane phospholipids were active in inhibiting the interaction of fusicoccin with its receptors. It is concluded that a phospholipid associated to the fusicoccin receptor might play a significant role in the modulation of binding.Fusicoccin; Membrane receptor; Zeu mays L.

A fusicoccin binding protein belongs to the family of 14-3-3 brain protein homologs.

“…Although it is evident now that the IAA and FC signal transduction pathways are rather different, it may well be that they share a common element. This can be inferred from a number of independent observations: (1) phospholipase A2, a G protein-coupled enzyme, induces the loss of high-affinity FC binding (Aducci et al, 1993a); (2) activation of G proteins results in the loss of high-affinity FC binding as well ; and (3) auxin activates phospholipase A*, which is most likely mediated by G proteins, ultimately leading to kinase activation (Scherer and André, 1993). These observations could be reconciled by postulating a working model in which a kinase, which mediates the auxin signal and is under direct control of the FCBP, plays a pivotal role in both signal transduction pathways.…”

Ligand binding inhibitors of A1 adenosine receptor from Rana rugosa are phospholipase A2s

“…As described previosuly, the partial reversal of inhibition by BSA suggests that fatty acids are also important factors in the inhibition. Lysophospholipids produced from the cleavage of membrane phospholipids by PLA 2 may also affect the ligand‐binding inhibition [27,29]. Therefore, since the membrane lipid bilayer is composed of fatty acids and phospholipids, the structure of the membrane may play a role in modulating A1 receptor activity, or PLA 2 itself may bind to the A1 receptor and competitively inhibit ligand binding.…”

“…To date, sPLA 2 has been generally used as a ligand‐binding modulator for various receptors. PLA 2 from bee venom showed an inhibitory effect on fusicoccin binding [29]. PLA 2 from porcine pancreas induced a significant increase in the binding of th‐[ 3 H]amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionate ([ 3 H]AMPA) in the stratum radiatum of the CA1 region of the hippocampus and in the stratum moleculare of the cerebellum [32].…”

A Calcium and Free Fatty Acid-Modulated Protein Kinase as Putative Effector of the Fusicoccin 14-3-3 Receptor

“…6). This inhibitory effect is specific for the cz's-unsaturated fatty acids, since saturated fatty acids have no effect on FC binding (Aducci et al, 1993). It is interesting that when PM vesicles were preincubated for 30 min with calphostin C (in a buffer containing 0.005% Triton X-100) [ 3 H]FC binding was inhibited by 40% at 10~5 M calphostin C (Fig.…”