Autophagy regulates the localization and degradation of p16^INK4a

Abstract

The tumor suppressor protein p16 INK4a (p16) is a well‐established hallmark of aging that induces cellular senescence in response to stress. Previous studies have focused primarily on p16 regulation at the transcriptional level; comparatively little is known about the protein's intracellular localization and degradation. The autophagy–lysosomal pathway has been implicated in the subcellular trafficking and turnover of various stress‐response proteins and has also been shown to attenuate age‐related pathologies, but it is unclear whether p16 is involved in this pathway. Here, we investigate the role of autophagy, vesicular trafficking, and lysosomal degradation on p16 expression and localization in human epithelial cells. Time‐lapse fluorescence microscopy using an endogenous p16‐mCherry reporter revealed that serum starvation, etoposide, and hydrogen peroxide stimulate autophagy and drive p16 recruitment to acidic cytoplasmic vesicles within 4 hr. Blocking lysosomal proteases with leupeptin and ammonium chloride resulted in the accumulation of p16 within lysosomes and increased total p16 levels suggesting that p16 is degraded by this pathway. Furthermore, autophagy blockers chloroquine and bafilomycin A1 caused p16 aggregation within stalled vesicles containing autophagosome marker LC3. Increase of p16 within these vesicles coincided with the accumulation of LC3‐II. Knockdown of autophagosome chaperone p62 attenuated the formation of p16 aggregates in lysosomes, suggesting that p16 is targeted to these vesicles by p62. Taken together, these results implicate the autophagy pathway as a novel regulator of p16 degradation and localization, which could play a role in the etiology of cancer and age‐related diseases.

Protective mechanism of FoxO1 against early brain injury after subarachnoid hemorrhage by regulating autophagy

“…Therefore, we designed another experiment, in which SAH rats treated with FoxO1 were intraperitoneally injected with RAP or CQ respectively. So far, most of the autophagy inducers discovered and widely used, such as RAP, a natural product, target the upstream of autophagy, which means that it can promote the occurrence of biological autophagosomes (Zhao H. et al., 2013 ), while CQ, as an autophagosome autophagy suppressor, can inhibit the occurrence of biological autophagosomes (Coryell et al., 2020 ). In our experiment, we found that both ad‐FoxO1 and RAP attenuated the injury of nerve function in rats during EBI after SAH, and this synergistic effect also further reduced cerebral edema and Evans blue extravasation, decreased hippocampus neuronal cell apoptosis, and declined inflammatory response.…”

Screening and identification of NOTCH1, CDKN2A, and NOS3 as differentially expressed autophagy-related genes in erectile dysfunction

“…The knockout of autophagosome chaperone p62 attenuated p16 aggregates in lysosomes, indicating that p16 targets these vesicles through p62. As the regulator of autophagy, p16 performs a key role in the etiology of cancer and dementia (Coryell et al, 2020). Moreover, advanced age is a critical risk factor for most chronic diseases and functional defects in humans.…”

The Intricate Interplay between Cell Cycle Regulators and Autophagy in Cancer

“…This pro-autophagic effect of p16 INK4A was shown to be RB-dependent in glioblastoma [ 44 ] and could be partially explained by the transcriptional regulation of autophagic genes by the E2F transcription factors (see the subsection “”). More recently, some studies emphasized that the autophagic process regulates p16 INK4A quantity and localization, indicating crucial cross-talks and feedbacks between the cell-cycle regulators and autophagy [ 45 , 46 , 47 ]. Interestingly, the role of p16 INK4A in autophagy seems to be interrelated with its role during cellular senescence [ 48 ].…”