Adaptor Protein LAPF Recruits Phosphorylated p53 to Lysosomes and Triggers Lysosomal Destabilization in Apoptosis

Abstract

Evidence suggests a functional association between the tumor suppressor p53 and apoptosis-involved organelle lysosome; however, the detailed mechanisms remain poorly understood. We recently reported that a lysosome-targeting protein, LAPF (lysosome-associated and apoptosis-inducing protein containing PH and FYVE domains), could initiate apoptosis of L929 cells through a lysosomal-mitochondrial pathway. In this study, we show that LAPF specifically interacted with phosphorylated p53 (Ser 15/18 ) both in vitro and in vivo, which could be enhanced by apoptotic stimuli, such as tumor necrosis factor A (TNF-A) and ionizing irradiation. The PH domain of LAPF and the transactivation domain of p53 mediated the interaction between both molecules. Phosphorylated p53 (Ser 15/18 ) could translocate to lysosomes before lysosomal membrane permeabilization (LMP) in LAPF-initiated and TNF-induced apoptosis. Silencing of LAPF expression abrogated lysosomal translocation of phosphorylated p53 (Ser 15/18 ), whereas silencing of p53 expression had no effect on lysosomal translocation of LAPF. Similar to that of LAPF silencing, silencing of endogenous p53 expression in L929 cells could significantly impair TNF-A-induced LMP and apoptosis. However, reexpression of wild-type p53, p53S15D (substitution of Ser 15 to Asp that mimics a phosphorylated state), and p53R175H (a transcription-deficient mutant) in p53-knockdown L929 cells could rescue the decrease in TNF-induced apoptosis. The data suggest that phosphorylated p53 (Ser 15/18 ) might translocate to lysosome via forming complexes with adaptor protein LAPF and subsequently result in LMP and apoptosis, which might be in a transcriptionindependent manner. [Cancer Res 2007;67(23):11176-85]

Cell sensitivity to oxidative stress is influenced by ferritin autophagy

“…It should be noted that in the presence of SIH, lysosomal rupture does not occur due to oxidative stress because lysosomal iron is then bound in a non-redox-active form [63]. Thus another reason needs to be found, perhaps one in line with the observation that p53-activation rapidly results in lysosomal rupture [66], and with the finding that a member (LAPF) of a newly discovered family of proteins localizes to lysosomes and induces LMP and ensuing apoptosis by anchoring the p53 protein to the lysosomal membrane [89,90]. Together these new results support the hypothesis that lysosomal destabilization and a lysosomal-mitochondrial cross talk [75] may be a much more general phenomenon in the initiation of apoptosis than previously considered.…”

Persistence of effector memory Th1 cells is regulated by Hopx

“…Pro-apoptotic genes were downregulated by Hopx, e.g. the lysosome-associated apoptosis-inducing protein Plekhf1 [46,47], and Sox4 (SRY-box containing gene 4), a sensor for DNA damage [48]. Together, the transcriptome analysis suggests that besides Fas-mediated apoptosis other death pathways could also be influenced by Hopx.…”

Lysosomal cell death at a glance

“…Furthermore, early LMP in TNF-treated fibrosarcoma cells (Li et al, 2007), embelin-treated colon cancer cells (Joy et al, 2010), as well as in cortical neurons exposed to D9-tetrahydrocannabinol or b-amyloid (Fogarty et al, 2010;Gowran and Campbell, 2008) depends on p53 and is associated with the localization of phospho-Ser15-p53 to the lysosomal membrane. The recruitment of phosphoSer15-p53 to the lysosomes depends on LAPF (LMP-inducing lysosome-associated apoptosis-inducing protein containing PH and FYVE domains) (Li et al, 2007). It will be of great interest to reveal the mechanism of action of these proteins and to investigate whether p53 and/or LAPF link other cellular signals to LMP.…”