ABA inhibits myristoylation and induces shuttling of the RGLG1 E3 ligase to promote nuclear degradation of PP2CA. (12th March 2019)

• Record Type: Journal Article
• Authors: Belda‐Palazon, Borja; Julian, Jose; Coego, Alberto; Wu, Qian; Zhang, Xu; Batistic, Oliver; Alquraishi, Saleh A.; Kudla, Joerg; An, Chengcai; Rodriguez, Pedro L.
• Is Part Of: Plant journal. Volume 98:Number 5(2019)
• Page Start: 813
• Page End: 825
• Publication Date: 2019-03-12
• Subjects: abscisic acid signaling -- RGLG1 -- E3 ligase -- protein phosphatase type 2C -- ubiquitination -- myristoylation -- shuttling -- Arabidopsis thaliana; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.14274
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: Hormone‐ and stress‐induced shuttling of signaling or regulatory proteins is an important cellular mechanism to modulate hormone signaling and cope with abiotic stress. Hormone‐induced ubiquitination plays a crucial role to determine the half‐life of key negative regulators of hormone signaling. For ABA signaling, the degradation of clade‐A PP 2Cs, such as PP 2 CA or ABI 1, is a complementary mechanism to PYR / PYL / RCAR ‐mediated inhibition of PP 2C activity. ABA promotes the degradation of PP 2 CA through the RGLG 1 E3 ligase, although it is not known how ABA enhances the interaction of RGLG 1 with PP 2 CA given that they are predominantly found in the plasma membrane and the nucleus, respectively. We demonstrate that ABA modifies the subcellular localization of RGLG 1 and promotes nuclear interaction with PP 2 CA . We found RGLG 1 is myristoylated in vivo, which facilitates its attachment to the plasma membrane. ABA inhibits the myristoylation of RGLG 1 through the downregulation of N‐myristoyltransferase 1 ( NMT 1 ) and promotes nuclear translocation of RGLG 1 in a cycloheximide‐insensitive manner. Enhanced nuclear recruitment of the E3 ligase was also promoted by increasing PP 2 CA protein levels and the formation of RGLG 1–receptor–phosphatase complexes. We show that RGLG 1 Gly2Ala mutated at the N‐terminal myristoylation site shows constitutive nuclear localization and causes an enhanced response to ABA and salt or osmotic stress. RGLG 1/5 can interact with certain monomeric ABA receptors, which facilitates the formation of nuclear complexes such as RGLG 1– PP 2 CA – PYL 8. In summary, we provide evidence that an E3 ligase can dynamically relocalize in response to both ABA and increased levels of its target, which reveals a mechanism to explain how ABA enhances RGLG 1– PP 2 CA interaction and hence PP 2 CA degradation. Significance Statement: The degradation of negative regulators is crucial for hormone signaling. ABA promotes the degradation of PP2CA through the RGLG1/5 E3 ligases and enhances the interaction of RGLG1/5 with PP2CA through an unknown mechanism. We show that ABA modifies the plasma membrane localization of RGLG1 by inhibiting its myristoylation and promoting cycloheximide‐insensitive nuclear translocation, which allows interaction with nuclear PP2CA‐receptor complexes. We explain how a hormone can modulate the interaction of an E3 ligase with its target.