Targeting of the FYVE domain to endosomal membranes is regulated by a histidine switch.
Specific recognition of phosphatidylinositol 3-phosphate [PtdIns3P] by the FYVE domain targets cytosolic proteins to endosomal membranes during key signaling and trafficking events within eukaryotic cells. Here, we show that this membrane targeting is regulated by the acidic cellular environment. Lowering the cytosolic pH enhances PtdIns3P affinity of the FYVE domain, reinforcing the anchoring of early endosome antigen 1 (EEA1) to endosomal membranes. Reversibly, increasing the pH disrupts phosphoinositide binding and leads to cytoplasmic redistribution of EEA1. pH dependency is due to a pair of conserved His residues, the successive protonation of which is required for PtdIns3P head group recognition as revealed by NMR. Substitution of the His residues abolishes PtdIns3P binding by the FYVE domain in vitro and in vivo. Another PtdIns3P-binding module, the PX domain of Vam7 and p40phox is shown to be pH-independent. This provides the fundamental functional distinction between the two phosphoinositide-recognizing domains. The presented mode of FYVE regulation establishes the unique function of FYVE proteins as low pH sensors of PtdIns3P and reveals the critical role of the histidine switch in targeting of these proteins to endosomal membranes.
Lee
Stephanie A
SA
Department of Pharmacology and Molecular Biology Program, University of Colorado Health Sciences Center, Aurora, CO 80045, USA.
Eyeson
Rosemary
R
Cheever
Matthew L
ML
Geng
Jinming
J
Verkhusha
Vladislav V
VV
Burd
Christopher
C
Overduin
Michael
M
Kutateladze
Tatiana G
TG
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D003600:Cytosol / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D006367:HeLa Cells; D006639:Histidine / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D021381:Protein Transport; D050825:Synaptosomal-Associated Protein 25; D014162:Transfection; D033921:Vesicular Transport Proteins
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; C494208:SNAP25 protein, human; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; C085072:neutrophil cytosol factor 40K; C055525:phosphatidylinositol 3-phosphate; D006639:Histidine