Vps9p CUE domain ubiquitin binding is required for efficient endocytic protein traffic.
Rab5 GTPases are key regulators of protein trafficking through the early stages of the endocytic pathway. The yeast Rab5 ortholog Vps21p is activated by its guanine nucleotide exchange factor Vps9p. Here we show that Vps9p binds ubiquitin and that the CUE domain is necessary and sufficient for this interaction. Vps9p ubiquitin binding is required for efficient endocytosis of Ste3p but not for the delivery of the biosynthetic cargo carboxypeptidase Y to the vacuole. In addition, Vps9p is itself monoubiquitylated. Ubiquitylation is dependent on a functional CUE domain and Rsp5p, an E3 ligase that participates in cell surface receptor endocytosis. These findings define a new ubiquitin binding domain and implicate ubiquitin as a modulator of Vps9p function in the endocytic pathway.
Davies
Brian A
BA
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Topp
Justin D
JD
Sfeir
Agnel J
AJ
Katzmann
David J
DJ
Carney
Darren S
DS
Tall
Gregory G
GG
Friedberg
Andrew S
AS
Deng
Li
L
Chen
Zhijian
Z
Horazdovsky
Bruce F
BF
D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers; D004705:Endocytosis; D056827:Endosomal Sorting Complexes Required for Transport; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D008969:Molecular Sequence Data; D011485:Protein Binding; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D017931:DNA Primers; D056827:Endosomal Sorting Complexes Required for Transport; D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; C099285:VPS9 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D043743:Ubiquitin-Protein Ligase Complexes; C469287:RSP5 protein, S cerevisiae