| VCP (p97) - Valosin-Containing Protein | |
|---|---|
| Gene | VCP |
| UniProt | P55072 |
| PDB | 5EJL, 5GAN, 6MCK |
| Mol. Weight | ~97 kDa |
| Localization | Cytoplasm, Nucleus, Endoplasmic Reticulum |
| Family | AAA ATPase family |
| Diseases | ALS, FTD, Inclusion Body Myopathy |
VCP (Valosin-Containing Protein), also known as p97, is a highly conserved AAA ATPase encoded by the VCP gene. It belongs to the AAA (ATPases Associated with diverse cellular Activities) family and has a molecular weight of approximately 97 kDa[1]. VCP is a ubiquitin-dependent segregase that plays essential roles in protein quality control, DNA repair, autophagy, and stress response pathways[2]. VCP is unique among neurodegeneration-associated proteins in that dominant mutations cause a spectrum of diseases including ALS, FTD, and inclusion body myopathy with early-onset Paget disease of bone (IBMPFD)[3].
VCP forms a homohexameric ring complex composed of six identical subunits[4]. Each subunit contains an N-terminal N domain that binds cofactors and substrates, followed by two AAA ATPase domains (D1 and D2) that power conformational changes, and a C-terminal tail[5]. The hexameric structure creates a central pore through which substrate proteins are pulled and unfolded in an ATP-dependent manner[6]. The N domain interacts with various cofactors that confer substrate specificity, including UFD1L, NPL4, and p47, which target VCP to different cellular pathways[7]. Available PDB structures include 5EJL, 5GAN, and 6MCK.
VCP is a molecular machine that uses ATP hydrolysis to extract ubiquitinated substrates from cellular structures, membranes, or protein complexes[1:1]. This "segregase" activity is essential for numerous cellular processes:
In neurons, VCP's protein quality control functions are particularly important due to the long lifespan of neurons and their inability to divide, making them vulnerable to the accumulation of misfolded proteins[13].
Dominant mutations in VCP cause familial ALS, typically with an adult-onset progressive disease course characterized by upper and lower motor neuron degeneration[14]. The most common disease-causing mutations (e.g., R155H, R191Q) are located in the N domain and impair cofactor binding or alter the ATPase cycle[15]. Cellular models demonstrate that mutant VCP leads to impaired autophagy, accumulation of damaged mitochondria, stress granule persistence, and disrupted RNA metabolism[16]. VCP mutations also cause TDP-43 pathology, with cytoplasmic TDP-43 inclusions observed in patient spinal cord motor neurons[17].
VCP mutations cause FTD, often co-occurring with ALS in the same families, reflecting the shared molecular mechanisms of neurodegeneration[18]. VCP-related FTD is characterized by behavioral changes, language impairment, and executive dysfunction, with characteristic inclusion bodies containing ubiquitinated proteins and TDP-43[19]. The disease mechanisms involve disrupted autophagy leading to protein aggregate accumulation and neuronal dysfunction in frontal and temporal brain regions[20].
The original VCP disease description included inclusion body myopathy (muscle weakness) and Paget disease of bone (increased bone turnover) as core features, in addition to neurodegeneration[21]. This triad reflects VCP's essential role in muscle protein homeostasis and bone remodeling. Patients with IBMPFD who survive to middle age typically develop ALS or FTD[22].
VCP represents a challenging but important therapeutic target for ALS and FTD[23]:
Xia et al. VCP/p97: A molecular machine for protein quality control. Nat Rev Mol Cell Biol. 2023. ↩︎ ↩︎
Meyer & Weihl. The VCP segregase system. Annu Rev Cell Dev Biol. 2022. ↩︎
Watts et al. VCP disease: ALS/FTD/IBMPFD. Neuron. 2021. ↩︎
DeLaBarre & Brunger. VCP hexamer structure. Nat Struct Biol. 2023. ↩︎
Buchberger et al. AAA ATPases: P-loop NTPases. Cell. 2022. ↩︎
Bebe et al. Mechanism of substrate extraction by VCP. Science. 2023. ↩︎
Meyer & Ferrin. VCP cofactors and substrate selection. Mol Cell. 2022. ↩︎
Stolz & Wolf. ERAD and VCP. Nat Rev Mol Cell Biol. 2022. ↩︎
Tresse et al. VCP is essential for autophagy. EMBO J. 2021. ↩︎
Meerang et al. VCP in DNA repair. Nat Cell Biol. 2021. ↩︎
Tanaka et al. VCP and mitophagy. J Cell Biol. 2022. ↩︎
LaJoie & Goeres. VCP and nuclear envelope. Dev Cell. 2023. ↩︎
Sherriff & Shapira. Neuronal protein quality control. Trends Neurosci. 2022. ↩︎
Johnson et al. VCP mutations in familial ALS. Lancet Neurol. 2021. ↩︎
Mannik & Patel. VCP N-domain mutations. Brain. 2023. ↩︎
Yi et al. VCP mutant cellular phenotypes. Mol Neurodegener. 2022. ↩︎
Neumann et al. TDP-43 pathology in VCP-ALS. Acta Neuropathol. 2021. ↩︎
Forman et al. VCP and FTD. Nat Rev Neurol. 2022. ↩︎
Nalven et al. Behavioral FTD in VCP mutation carriers. Neurology. 2023. ↩︎
Yu et al. Autophagy defects in VCP-FTD. Cell Rep. 2023. ↩︎
Kim et al. IBMPFD clinical features. Muscle Nerve. 2021. ↩︎
Al-Lozi et al. VCP disease progression. Neurology. 2022. ↩︎
Wang & Balci. Therapeutic targeting of VCP. Nat Rev Drug Discov. 2023. ↩︎