title: Valosin-containing protein (VCP/p97) is capable of unfolding polyubiquitinated proteins through its ATPase domains.
abstract: Valosin-containing protein (VCP or p97) is required for the proteasomal degradation of polyubiquitinated proteins. However, the molecular mechanism for VCP to process the polyubiquitinated proteins remains unclear. Here, we show that VCP can unfold polyubiquitinated proteins. It preferably unfolds the pentaubiquitin-over monoubiquin-conjugated dihydrofolate reductase (Ub5-DHFR or Ub-DHFR) in a dose dependent manner. In addition, the unfolding activity of VCP does not depend on its ATPase activity, on the contrary, ATP and its non-hydrolysable analogs suppress the unfolding of Ub5-DHFR. The structural and functional analysis showed that either D1 or D2 domain of VCP is sufficient to carry out this unfolding activity. The structure of the substrates also affects its unfolding by VCP. VCP is unable to unfold Ub5-DHFR in a tight structure when it binds with methotrexate, a folate analog with high affinity to DHFR. Thus, these results support that VCP is capable of unfolding polyubiquitinated proteins and suggest that VCP may facilitate the proteasomal degradation of polyubiquitinated proteins through its unfolding activity.
authors.affiliation: Center for Inflammation, Translational and Clinical Lung Research, School of Medicine, Temple University, Philadelphia, PA 19140, USA. Electronic address: songc@temple.edu.
authors.forename: Changcheng
authors.initials: C
authors.lastname: Song
authors.affiliation: Graduate Center for Toxicology, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Erythrocrine Project of Translational Medicine, Shandong Academy of Medical Sciences, Jinan 250062, China.
authors.forename: Changzheng
authors.initials: C
authors.lastname: Song
authors.affiliation: Center for Inflammation, Translational and Clinical Lung Research, School of Medicine, Temple University, Philadelphia, PA 19140, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Rogers
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002918:Chymotrypsin / Q000378:metabolism; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D054875:Ubiquitination; D000074405:Valosin Containing Protein
chemical_list: D018797:Cell Cycle Proteins; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D013762:Tetrahydrofolate Dehydrogenase; D002918:Chymotrypsin; D000251:Adenosine Triphosphatases; D000074405:Valosin Containing Protein
keywords: ATPase; Polyubiquitinated protein; Structure and functional analysis; Unfolding; Valosin-containing protein (VCP or p97)