VPS34 stimulation of p62 phosphorylation for cancer progression

Abstract

Vps34, a class III PtdIns3 lipid kinase involved in the control of both autophagic and endocytic systems, has been studied extensively in numerous fundamental cellular processes. Accumulating evidence indicates that Vps34 may also contribute to the development and progression of human cancers. However, the mechanism of Vps34 in tumorigenesis remains elusive. Here, we report an unanticipated role of Vps34 in the activation of p62 for cancer development. We identified that Vps34 is a transcriptional activator of p62 through competition of Nrf2 (nuclear factor erythroid 2-related factor 2) for Keap1 binding. Vps34 augments the association of PKC-δ with p62 for its phosphorylation at Serine 349, which leads to positive feedback on the Nrf2-dependent transcription of oncogenes. Additionally, we found that the expression of Vps34 is correlated with the tumorigenic activity of human breast cancer cells. Normally inactive in breast cancer, caspase 8 can cleave Vps34 at residue D285, which directly abolished its lipid kinase activity and dramatically altered cell invasion potential, colony formation, as well as tumorigenesis in orthotopic engraftments in mice. The cleavage at D285 blocks expression of LC3-II, Nrf2 and subsequently, p62, in addition to blocking tumor growth, indicating that the intact structure of Vps34 is essential for its activity. Moreover, either knockout of PKC-δ or knockdown of p62 by small interfering RNA in MCF-7 cells abrogates Vps34-dependent tumor growth. Data presented here suggested that Vps34 stimulates tumor development mainly through PKC-δ- activation of p62.

p62/SQSTM1 – steering the cell through health and disease

“…3B, step 3) (Ichimura et al, 2013;Komatsu et al, 2010). Multiple kinases, including casein kinase 1 (CSNK1A1), transforming growth factor beta-activated kinase 1 (TAK1, officially known as MAP3K7), mTORC1 and PKC-delta (PRKCD), promote this phosphorylation during selective autophagy (Hashimoto et al, 2016;Ichimura et al, 2013;Jiang et al, 2017;Watanabe et al, 2017).…”

Autophagy inhibition potentiates the anti-EMT effects of alteronol through TGF-β/Smad3 signaling in melanoma cells

“…Cell viability and colony formation assay were performed as described previously 21,22 . Briefly, cells were seeded in 96-well plates (5000 cells/well) and then were subjected to various indicated treatments.…”

“…mCherry-EGFP-LC3 stable cell line were generated by using a mCherry-EGFP-LC3 plasmid purchased from Addgene (#22418). CRISPR/Cas9 KO system and mCherry-EGFP-LC3 stable cell line were performed as described previously 21 . The recombinant lentivirus encoding mCherry-EGFP-LC3 or lentiCRISPRv2-Beclin1 produced by 293 T cells were used to transduce A375 or UACC62 cells.…”

“…Autophagy was measured by quantifying the number of yellow or red puncta in mCherry-EGFP-LC3 stable cell lines 21 treated with or without alteronol. Images acquisition was performed by using LSM710 confocal microscope with a ×63 oil objective (Carl Zeiss).…”

“…Cell migration or invasion was measured by using Cultrex® 96 Well Cell Migration Assay or Cultrex® 96 Well BME Cell Invasion Assay (Trevigen, USA) according to a standard protocol 21 . Briefly, cells (5 × 10 4 cells/well) were trypsinized and seed on the upper chamber of a transwell (migration) or a 1xBME solution-coated transwell (invasion) in serum-free media.…”