Valosin-containing protein (p97) is a regulator of endoplasmic reticulum stress and of the degradation of N-end rule and ubiquitin-fusion degradation pathway substrates in mammalian cells.
Valosin-containing protein (VCP; p97; cdc48 in yeast) is a hexameric ATPase of the AAA family (ATPases with multiple cellular activities) involved in multiple cellular functions, including degradation of proteins by the ubiquitin (Ub)-proteasome system (UPS). We examined the consequences of the reduction of VCP levels after RNA interference (RNAi) of VCP. A new stringent method of microarray analysis demonstrated that only four transcripts were nonspecifically affected by RNAi, whereas approximately 30 transcripts were affected in response to reduced VCP levels in a sequence-independent manner. These transcripts encoded proteins involved in endoplasmic reticulum (ER) stress, apoptosis, and amino acid starvation. RNAi of VCP promoted the unfolded protein response, without eliciting a cytosolic stress response. RNAi of VCP inhibited the degradation of R-GFP (green fluorescent protein) and Ub-(G76V)-GFP, two cytoplasmic reporter proteins degraded by the UPS, and of alpha chain of the T-cell receptor, an established substrate of the ER-associated degradation (ERAD) pathway. Surprisingly, RNAi of VCP had no detectable effect on the degradation of two other ERAD substrates, alpha1-antitrypsin and deltaCD3. These results indicate that VCP is required for maintenance of normal ER structure and function and mediates the degradation of some proteins via the UPS, but is dispensable for the UPS-dependent degradation of some ERAD substrates.
Wójcik
Cezary
C
Department of Anatomy and Cell Biology, Indiana University School of Medicine, Evansville, IN 47712, USA.
Rowicka
Maga
M
Kudlicki
Andrzej
A
Nowis
Dominika
D
McConnell
Elizabeth
E
Kujawa
Marek
M
DeMartino
George N
GN
D000251:Adenosine Triphosphatases; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000473:pathology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008322:Mammals / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013379:Substrate Specificity; D014158:Transcription, Genetic; D014452:Ubiquitins / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics; D014617:Vacuoles / Q000648:ultrastructure; D000074405:Valosin Containing Protein
D018797:Cell Cycle Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014452:Ubiquitins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C000614178:VCP protein, human; D000074405:Valosin Containing Protein