A plant peptide: N-glycanase orthologue facilitates glycoprotein ER-associated degradation in yeast.
BACKGROUND
The cytoplasmic peptide:N-glycanase (PNGase) is a deglycosylating enzyme involved in the ER-associated degradation (ERAD) process, while ERAD-independent activities are also reported. Previous biochemical analyses indicated that the cytoplasmic PNGase orthologue in Arabidopsis thaliana (AtPNG1) can function as not only PNGase but also transglutaminase, while its in vivo function remained unclarified.


METHODS
AtPNG1 was expressed in Saccharomyces cerevisiae and its in vivo role on PNGase-dependent ERAD pathway was examined.


RESULTS
AtPNG1 could facilitate the ERAD through its deglycosylation activity. Moreover, a catalytic mutant of AtPNG1 (AtPNG1(C251A)) was found to significantly impair the ERAD process. This result was found to be N-glycan-dependent, as the AtPNG(C251A) did not affect the stability of the non-glycosylated RTA∆ (ricin A chain non-toxic mutant). Tight interaction between AtPNG1(C251A) and the RTA∆ was confirmed by co-immunoprecipitation analysis.


CONCLUSIONS
The plant PNGase facilitates ERAD through its deglycosylation activity, while the catalytic mutant of AtPNG1 impair glycoprotein ERAD by binding to N-glycans on the ERAD substrates.


CONCLUSIONS
Our studies underscore the functional importance of a plant PNGase orthologue as a deglycosylating enzyme involved in the ERAD.
Glycometabolome Team, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Yuki
Y
Masahara-Negishi
Akira
A
Hosomi
Massimiliano
M
Della Mea
Donatella
D
Serafini-Fracassini
Tadashi
T
Suzuki
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D060746:Endoplasmic Reticulum-Associated Degradation / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D006023:Glycoproteins / Q000378:metabolism*; D006031:Glycosylation / Q000187:drug effects; D008969:Molecular Sequence Data; D030781:Organisms, Genetically Modified; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology* / Q000502:physiology; D010944:Plants / Q000201:enzymology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics; D017385:Sequence Homology; D014162:Transfection; D015003:Yeasts / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D006023:Glycoproteins; D029701:Saccharomyces cerevisiae Proteins; C468820:PNG1 protein, S cerevisiae; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase