WW Domain-containing E3 Ubiquitin Protein Ligase 1 (WWP1) Delays Cellular Senescence by Promoting p27Kip1 Degradation in Human Diploid Fibroblasts

Abstract

WW domain-containing E3 ubiquitin protein ligase 1 (WWP1) plays an important role in the proliferation of tumor cells and the lifespan of Caenorhabditis elegans. However, the role of WWP1 in cellular senescence is still unknown. Here, we show that the expression patterns of p27 Kip1 and WWP1 are inversely correlated during cellular senescence. Moreover, the overexpression of WWP1 delayed senescence, whereas the knockdown of WWP1 led to premature senescence in human fibroblasts. Furthermore, we demonstrate that WWP1 repressed endogenous p27Kip1 expression through ubiquitin-proteasome-mediated degradation. Additionally, WWP1 had a strong preference for catalyzing the Lys-48-linked polyubiquitination of p27 Kip1 in vitro. Finally, we demonstrate that WWP1 markedly inhibited the replicative senescence induced by p27Kip1 by promoting p27 Kip1 degradation. Therefore, our study provides a new molecular mechanism for the regulation of cellular senescence.The concept of replicative senescence is based on the inability of cells to divide indefinitely in culture. Instead, the cells enter an irreversible state of proliferative arrest with specific associated changes in cellular morphology and gene expression. The senescent phenotype is characterized by growth inhibition with enlarged and flattened cellular morphology (1), highly active senescence-associated ␤-galactosidase (SA-␤-gal) 2 (2), and the accumulation of senescence-associated heterochromatin foci (SAHF) (3, 4). In a sense, cellular senescence is a reflection of organism aging, and investigation into replicative senescence may thus provide information about the molecular mechanisms of organism senescence and aging-related diseases. In recent years, increasing numbers of molecular mechanisms of cellular senescence have been studied. It is well accepted that there are three pathways that play key roles in replicative senescence, namely the p16INK4a pathway, the p53/ p21Cip1 pathway, and the p27 Kip1 pathway (5). However, in comparison with the first two pathways, relatively few studies have focused on the p27 Kip1 pathway. The majority of proteins involved in replicative senescence are modified by polyubiquitin, which directs proteins for degradation by the 26 S proteasome. For example, cyclin-dependent kinase inhibitors, which are of special relevance to senescence, are mainly regulated by the ubiquitin-proteasome system. The ubiquitination cascade operates by the sequential action of the E1, E2, and E3 enzymes. E3 ubiquitin ligases are significant in cellular regulation because E3 enzymes specifically recognize the substrate to be modified. It is well established that the E3 enzymes control substrate specificity. WW domain-containing E3 ubiquitin protein ligase 1 (WWP1) is an E3 ubiquitin ligase first identified by its WW domain (6). WWP1 belongs to the Nedd4-like family of E3 ubiquitin ligases, a subfamily of HECT, which contains Nedd4, Itch, WWP2, AIP4, and RPF1 (7, 8). Members of this family have been shown to be involved in the regulation of cellular signaling...

WWP1: a versatile ubiquitin E3 ligase in signaling and diseases

“…It is possible that the induction of WWP1 by TGFb is a negative feedback mechanism for controlling the TGFb signaling pathway since WWP1 suppresses TGFb signaling [1,22]. During the cellular senescence, WWP1 has been shown to be downregulated [30].…”

“…In addition, WWP1 overexpression promoted breast epithelial cell growth and anchorageindependent growth [24]. In 2BS and WI38 fibroblast cell lines, overexpression of WWP1 increased cell proliferation while depletion of WWP1 induced senescence [30]. WWP1 enhances cell proliferation and survival likely through both ubiquitin ligase-dependent and -independent activities.…”

“…It would be interesting to elucidate the role and mechanism of action of WWP1 in mammalian longevity. Most recently, Cao et al [30] reported that the expression level of WWP1 in young human fibroblasts is significantly higher than that in aged fibroblasts with senescence. Further investigation revealed that WWP1 targets the cell cycle-dependent kinase inhibitor p27 kip protein for ubiquitin-mediated degradation in human fibroblasts [30].…”

Megalin-Mediated Tubuloglomerular Alterations in High-Fat Diet–Induced Kidney Disease

“…19 In intravital imaging in kidneys of HFD-fed wild-type mice using two-photon laser scanning microscopy, abnormal autofluorescence was found in PTECs ( Figure 2C) that were located in the S2 segment ( Supplemental Figure 3). The intracellular distribution and tubular localization patterns of the autofluorescent substances indicated that they were contained in dysfunctional autolysosomes of PTECs.…”

WWP1 as a potential tumor oncogene regulates PTEN-Akt signaling pathway in human gastric carcinoma

“…WWP1 harbors three various domains, including four tandem WW domains, an N-terminal C2 domain, and a homologous E6AP carboxy terminus (HECT) region [13,14], which encodes 922 amino acid residues with the molecular weight of 110 kDa [15]. Accumulating evidence has showed that WWP1 is implicated in the regulation of a variety of biological processes, such as protein trafficking and degradation, signaling transduction, cellular senescence, transcription, and viral budding [15][16][17][18]. Currently, more and more studies have revealed that WWP1 plays pivotal roles in the occurrence, development, progression, and prognosis of many tumors including hepatocellular carcinoma [19], oral cancer [20], breast carcinoma [9], and prostate cancer [4].…”