title: The sequence NPFXD defines a new class of endocytosis signal in Saccharomyces cerevisiae.
abstract: The yeast membrane protein Kex2p uses a tyrosine-containing motif within the cytoplasmic domain for localization to a late Golgi compartment. Because Golgi membrane proteins mislocalized to the plasma membrane in yeast can undergo endocytosis, we examined whether the Golgi localization sequence or other sequences in the Kex2p cytoplasmic domain mediate endocytosis. To assess endocytic function, the Kex2p cytoplasmic domain was fused to an endocytosis-defective form of the alpha-factor receptor. Ste2p. Like intact Ste2p, the chimeric protein, Stex22p, undergoes rapid endocytosis that is dependent on clathrin and End3p. Uptake of Stex22p does not require the Kex2p Golgi localization motif. Instead, the sequence NPFSD, located 37 amino acids from the COOH terminus, is essential for Stex22p endocytosis. Internalization was abolished when the N, P, or F residues were converted to alanine and severely impaired upon conversion of D to A. NPFSD restored uptake when added to the COOH terminus of an endocytosis-defective Ste2p chimera lacking lysine-based endocytosis signals present in wild-type Ste2p. An NPF sequence is present in the cytoplasmic domain of the a-factor receptor, Ste3p. Mutation of this sequence prevented pheromone-stimulated endocytosis of a truncated form of Ste3p. Our results identify NPFSD as a clathrin-dependent endocytosis signal that is distinct from the aromatic amino acid-containing Golgi localization motif and lysine-based, ubiquitin-dependent endocytosis signals in yeast.
authors.affiliation: Department of Biological Chemistry, UCLA School of Medicine 90095, USA.
authors.forename: P K
authors.initials: PK
authors.lastname: Tan
authors.forename: J P
authors.initials: JP
authors.lastname: Howard
authors.forename: G S
authors.initials: GS
authors.lastname: Payne
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001692:Biological Transport / Q000502:physiology; D002966:Clathrin / Q000502:physiology; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000502:physiology; D004705:Endocytosis / Q000502:physiology*; D005656:Fungal Proteins / Q000737:chemistry / Q000502:physiology; D006056:Golgi Apparatus / Q000737:chemistry / Q000502:physiology; D018257:Helix-Loop-Helix Motifs / Q000502:physiology; D007150:Immunohistochemistry; D008074:Lipoproteins / Q000737:chemistry / Q000502:physiology; D008239:Lysine / Q000502:physiology; D010675:Pheromones / Q000737:chemistry / Q000378:metabolism; D043484:Proprotein Convertases; D021382:Protein Sorting Signals / Q000032:analysis / Q000502:physiology*; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide / Q000737:chemistry / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000502:physiology; D012097:Repressor Proteins / Q000737:chemistry / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D013381:Subtilisins / Q000737:chemistry / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics; D014443:Tyrosine / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D002966:Clathrin; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C091908:END3 protein, S cerevisiae; D005656:Fungal Proteins; D008074:Lipoproteins; C095063:MFA2 protein, S cerevisiae; D010675:Pheromones; D021382:Protein Sorting Signals; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C081863:STE3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D014443:Tyrosine; D043484:Proprotein Convertases; D013381:Subtilisins; C058751:KEX2 protein, S cerevisiae; D008239:Lysine