Tyrosine phosphorylation of ATPase p97 regulates its activity during ERAD.
In eukaryotic cells, the endoplasmic reticulum-associated degradation (ERAD) pathway is essential for the disposal of misfolded proteins. Recently, we demonstrated the existence of a higher order complex consisting of the ER bound E3 ligase gp78, p97, PNGase, and HR23B in mammals. This complex may serve to facilitate the routing of misfolded glycoproteins out of the ER to the cytosol where they are degraded by the proteasome. In this complex, p97 functions as an organizer to mediate the interactions with gp78 and the deglycosylating enzyme PNGase. A novel protein-binding motif of mouse p97 was identified that consists of its last 10 amino acid residues; this motif is sufficient to mediate the interaction of p97 with PNGase and Ufd3. Phosphorylation of p97's highly conserved penultimate tyrosine residue, completely blocks binding of both PNGase and Ufd3 to mp97. We have found that c-Src kinase directly and selectively phosphorylated the penultimate tyrosine of p97 in vitro, and that overexpression of c-Src significantly increased the phosphorylation level of p97 in cells and caused accumulation of the ERAD substrate TCRalpha-GFP, as well as ubiquitin-conjugated substrates. These results suggest a role for p97 phosphorylation in the degradation of misfolded glycoproteins.
Li
Guangtao
G
Department of Biochemistry and Cell Biology, 450 Life Science Building, Stony Brook University, Stony Brook, NY 11794-5215, USA.
Zhao
Gang
G
Schindelin
Hermann
H
Lennarz
William J
WJ
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000081247:CSK Tyrosine-Protein Kinase; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D017510:Protein Folding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012276:Ricin / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D019061:src-Family Kinases
D006023:Glycoproteins; D009687:Nuclear Proteins; D025801:Ubiquitin; D014443:Tyrosine; D012276:Ricin; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D000251:Adenosine Triphosphatases; C404942:p97 ATPase