On the role of major vault protein in the resistance of senescent human diploid fibroblasts to apoptosis

Abstract

Major vault protein (MVP), the main component of vault complex, is overexpressed in many multidrug-resistant cancer cell lines, suggesting a possible role for MVP in cell signaling and survival. In this study, we have found that MVP is markedly increased in senescent human diploid fibroblasts (HDFs) as well as in aged organs. We examined whether MVP expression might be affected by apoptotic stress in an aging-dependent manner. We treated young and senescent HDFs with apoptosis-inducing agents such as H 2 O 2 , staurosporine and thapsigargin, and monitored MVP expression. We found that MVP expression is markedly reduced in young HDFs but not in senescent HDFs, in response to apoptotic stresses. Downregulation of MVP increased the sensitivity of senescent HDFs to apoptosis. Also, the level of antiapoptotic B-cell lymphoma protein-2 (Bcl-2) was significantly reduced and the accumulation of c-Jun increased in MVP knocked-down senescent HDFs. Moreover, treatment of MVP knocked-down senescent HDFs with SP600125, a specific c-Jun NH (2) Vaults are large ribonucleoprotein particles found in a great portion of eukaryotic cells. The vault particle is a multimeric structure composed of three proteins -the major vault protein (MVP), two minor vault proteins, vault poly (ADP-ribose) polymerase (VPARP) and telomerase-associated protein-1 (TP-1), and four small untranslated vault RNAs (vRNAs). 1 MVP is the main component of the vault complex accounting for 75% of the total particle mass. 2 The vault particle has been so named because it has a barrel-shaped structure, reminiscent of the vaulted ceilings in cathedrals. 3 The interaction of MVP by its coiled coil domain is involved in the formation of the basic vault complex. 4 MVP expression is upregulated in cancers such as melanoma, 5 colon cancer 6 and gliomas 7 during acquisition of multidrug resistance 8,9 and during differentiation of dendritic cells. 10 MVP expression has also been shown to be induced by histone deacetylase inhibitors such as sodium butyrate, 11 phorbol 12-myristate 13-acetate (PMA) and cytarabine 12 as well as by cytotoxic drugs. 12-14 MVP/vaults have been proposed to be important in intracellular transport, 15-17 innate immunity 18 and virus infection. 19 Several studies demonstrated that MVP is important in cell signaling [20][21][22] and in cell survival. 10,20,23 For example, serumdeprived MVP-deficient mouse embryonic fibroblasts (MEFs) exhibit significantly increased cell death when compared with wild-type MEFs. 20 Therefore, the role of MVP as a scaffolding protein for signaling proteins, especially for cell survival, has received more attention than as a transport vehicle. However, the exact role of MVP in cell survival is not well understood. In this study, we found that apoptotic resistance of senescent human diploid fibroblasts (HDFs) correlates with the increased content of MVP in the senescent cells. This is the first report implicating MVP in apoptosis resistance of senescent HDFs. ResultsIncreased expression of MVP in aged cells and organs...

Major Vault Protein Regulates Class A Scavenger Receptor-mediated Tumor Necrosis Factor-α Synthesis and Apoptosis in Macrophages

“…On the other hand, Dortet et al have suggested that MVP may, by interacting with the bacterial protein InlK, facilitate the evasion of opportunistic bacterium by impairing the formation of autophagous vesicles (32). Similarly, we demonstrate here that a SR-A-MVP-caveolin complex serves as a prerequisite for apoptosis in macrophages whereas Ryu et al have reported that MVP affords senescent fibroblast cells the resistance to oxidative stress induced apoptosis (23). The two seemingly distinct aspects of MVP activity are probably indications of its flexibility in mediating cellular events.…”

“…MVP expression and/or activity is known to fluctuate according to environmental signals, essentially positioning MVP as a stress protein (21)(22)(23)(24). It has been proposed to carry out important pathobiologi- cal functions in drug resistance, intracellular transport, cellular differentiation, innate immunity, virus infections, and cell survival (25,26).…”

Proteomic Analysis Reveals a Role for Bcl2-associated Athanogene 3 and Major Vault Protein in Resistance to Apoptosis in Senescent Cells by Regulating ERK1/2 Activation

“…Among the Bag3 novel interactors, we identified MVP and associated proteins, which form a protein complex that is strongly associated with chemotherapy resistance. MVP has been recently described as associated with resistance to apoptosis in senescent fibroblasts (33). We demonstrated that MVP gene-silencing switches the response from senescence to apoptosis.…”

Differential Expression of Extracellular Matrix Proteins in Senescent and Young Human Fibroblasts: a Comparative Proteomics and Microarray Study

“…In contrast to dividing cells, senescent cells display characteristic phenotypic alterations such as an increase in the expression of cell cycle inhibitory molecules (Demidenko and Blagosklonny, 2008), a large and flat morphology (Cho et al, 2004), higher senescence-associated β-galactosidase activity (SA-β-gal) (Dimri et al, 1995;Kang et al, 2009), accumulation of oxidative damage (Harman, 1956), hypo-responsiveness to growth factors (Kim et al, 2010) and apoptotic resistance (Ryu et al, 2008). In various cellular processes, morphological changes play an important role in cellular function.…”