Phosphatidylinositol 3-phosphate–binding protein AtPH1 controls the localization of the metal transporter NRAMP1 in Arabidopsis

Abstract

"Too much of a good thing" perfectly describes the dilemma that living organisms face with metals. The tight control of metal homeostasis in cells depends on the trafficking of metal transporters between membranes of different compartments. However, the mechanisms regulating the location of transport proteins are still largely unknown. Developing seedlings require the natural resistance-associated macrophage proteins (NRAMP3 and NRAMP4) transporters to remobilize iron from seed vacuolar stores and thereby acquire photosynthetic competence. Here, we report that mutations in the pleckstrin homology (PH) domain-containing protein AtPH1 rescue the iron-deficient phenotype of Our results indicate that AtPH1 binds phosphatidylinositol 3-phosphate (PI3P) in vivo and acts in the late endosome compartment. We further show that loss of AtPH1 function leads to the mislocalization of the metal uptake transporter NRAMP1 to the vacuole, providing a rationale for the reversion of phenotypes. This work identifies a PH domain protein as a regulator of plant metal transporter localization, providing evidence that PH domain proteins may be effectors of PI3P for protein sorting.

Intracellular Distribution of Manganese by the Trans-Golgi Network Transporter NRAMP2 Is Critical for Photosynthesis and Cellular Redox Homeostasis

“…Since endocytosed plasma membrane proteins are initially targeted to early endosomes, and since the TGN can also function as an early endosome in plants (Uemura and Nakano, 2013), a possibility existed that NRAMP2 was in fact cycling between the plasma membrane and TGN. Interestingly, dual targeting of NRAMP1 between the plasma membrane and intracellular vesicles of the endomembrane pathway was recently reported (Agorio et al, 2017). Unlike NRAMP1, however, we did not find evidence for the presence of NRAMP2 at the cell surface, regardless of whether NRAMP2-GFP-expressing plants were Mn starved or treated with the endocytosis inhibitor Tyrphostin A23.…”

Sorting of Arabidopsis NRAMP3 and NRAMP4 depends on adaptor protein complex AP4 and a dileucine‐based motif

“…A similar scenario, for example, accounts for the polar sorting of AMPA receptors in neurons, which depends on the interaction between AP4μ and a transmembrane AMPA receptor regulatory protein, which in turn interacts with the receptor . Localization of Arabidopsis NRAMP1 was recently shown to be dependent on a PH domain‐containing protein, AtPH1; more precisely, on the ability of AtPH1 to bind phosphatidylinositol 3‐phosphate . For one, this example contributes to the idea of a possible mechanism, which involves additional proteins mediating between NRAMP proteins and AP complex(es).…”

“…73 Localization of Arabidopsis NRAMP1 was recently shown to be dependent on a PH domain-containing protein, AtPH1; more precisely, on the ability of AtPH1 to bind phosphatidylinositol 3phosphate. 74 For one, this example contributes to the idea of a possible mechanism, which involves additional proteins mediating between NRAMP proteins and AP complex(es). And second, it may indicate the importance of specific phospholipid environments for APmediated protein sorting in plants.…”

Aspergillus nidulans BapH is a RAB11 effector that connects membranes in the Spitzenkörper with basal autophagy

“…The BAR‐PH cDNA fragment subcloned in pGEX‐2T encoded residues Gly40 through Thr433 of BapH. Lipid blots were carried out essentially as described (Agorio et al ., ). GST fusion proteins, purified with glutathione‐Sepharose affinity columns, were incubated with PIP arrays (P‐6001, Echelon Biosciences Inc., Salt Lake City, USA) containing purified lipids spotted on a hydrophobic membrane.…”