Disease relevance of Vcp

• A 97-kDa protein called valosin-containing protein (VCP) has been implicated in osteosarcoma metastasis and Paget's disease of bone, two conditions that complicate the course and outcome of orthopaedic surgery [1].
• High VCP gene expression is associated with high metastatic potential in osteosarcoma cells, while loss-of-function VCP mutations cause inclusion body myopathy associated with Paget's disease of bone and frontotemporal dementia (IBMPFD) [1].

High impact information on Vcp

• Here we demonstrate that another member of this family, Cdc48 in yeast and p97 in mammals, is required for the export of ER proteins into the cytosol [2].
• Mass spectrometry of crosslinked synaptotagmin . p97/VCP revealed interactions near Trp551 and Phe552 [3].
• The AAA-ATPase p97/VCP facilitates protein dislocation during endoplasmic reticulum-associated degradation (ERAD) [3].
• Given the D1 and D2 packing arrangement, we propose a ratchet mechanism for p97 during its ATP hydrolysis cycle [4].
• p97, an abundant hexameric ATPase of the AAA family, is involved in homotypic membrane fusion [4].

Biological context of Vcp

• Sequence analysis has shown VCP to be a member of a family of ATP binding, homo-oligomeric proteins, and the mammalian homolog of Saccharomyces cerevisiae cdc48p, a protein essential to the completion of mitosis in yeast [5].
• Deletion of this loop and point mutations in the loop significantly reduce p97 binding [6].
• Clones representing two distinct p97 genes were isolated in a genomic library screen, one of them likely representing a non-functional processed pseudogene [7].
• The mouse p97 (CDC48) gene. Genomic structure, definition of transcriptional regulatory sequences, gene expression, and characterization of a pseudogene [7].
• To examine the functional relevance of the p97 interaction with IP(3) receptors, we stably and specifically reduced p97 protein levels by 62 +/- 3% in Rat-1 fibroblasts using RNA interference [8].

Anatomical context of Vcp

• We also provide proof that both endogenous and expressed murine VCP are tyrosine phosphorylated in response to T cell activation [5].
• Inclusion body myopathy-associated mutations in p97/VCP impair endoplasmic reticulum-associated degradation [9].
• However, when expressed in cultured cells, both this and a second IBMPFD-associated p97/VCP mutant increase the overall level of ubiquitin-conjugated proteins and specifically impair degradation of mutant DeltaF508-CFTR handled by the ERAD pathway [9].
• The purpose of these studies was to characterize VCP protein expression in control and stressed untransformed osteoblasts [1].
• When assessed by indirect immunofluorescence in fixed cells or Western blotting of subcellular fractions, VCP was more abundant in the cytoplasm than in the nucleus [1].

Associations of Vcp with chemical compounds

• Small-angle X-ray scattering (SAXS) measurements of p97 in the presence of AMP-PNP (ATP state), ADP-AlF(x) (hydrolysis transition state), ADP, or no nucleotide reveal major changes in the positions of the N domains with respect to the hexameric ring during the ATP hydrolysis cycle [10].

Physical interactions of Vcp

• Wild-type Ube4b also requires N16 to bind VCP, despite a more C-terminal binding site in invertebrate orthologues [11].
• In order to provide insight into the molecular basis of p97 adaptor binding, we have determined the crystal structure of p97 ND1 domains complexed with p47 C-terminal domain at 2.9 A resolution [6].
• The crystal structure of the N-terminal domain of PNGase in complex with this motif provides detailed insight into the interaction between p97 and its substrate-processing cofactors [12].
• We assigned the backbone amides of the p97 N domain and probed both its reciprocal binding surface with Npl4 UBD and its interaction with the p97-binding region of Ufd1 [13].

Other interactions of Vcp

• We conclude that N-terminal sequences of Wld(S) protein influence the intranuclear location of both ubiquitin proteasome and NAD(+) synthesis machinery and that an evolutionary recent sequence mediates binding of mammalian Ube4b to VCP [11].
• In the latter, the p97 adaptor protein p47 is of central importance [6].
• In addition, Ufd1 and Npl4, which complex with p97, also associated with IP(3) receptors upon hormonal stimulation [8].
• The slow Wallerian degeneration protein, WldS, binds directly to VCP/p97 and partially redistributes it within the nucleus [11].
• Interaction with Wld(S) targets VCP to discrete intranuclear foci where ubiquitin epitopes can also accumulate [11].

Analytical, diagnostic and therapeutic context of Vcp

• Here, we report two structures: a crystal structure of the N-terminal and D1 ATPase domains of murine p97 at 2.9 A resolution, and a cryoelectron microscopy structure of full-length rat p97 at 18 A resolution [4].
• High constitutive VCP protein expression in subconfluent and confluent resting and mildly physiologically stressed MC3T3-E1 cells was confirmed by Western blotting [1].
• An abundant spot with a M(r) of 94 kDa and a pI of 5.4 was identified as VCP by MALDI/ToF and peptide mass fingerprint analysis [1].

References