The Vacuolar H+ ATPase α3 Subunit Negatively Regulates Migration and Invasion of Human Pancreatic Ductal Adenocarcinoma Cells

Abstract

Increased metabolic acid production and upregulation of net acid extrusion render pH homeostasis profoundly dysregulated in many cancers. Plasma membrane activity of vacuolar H+ ATPases (V-ATPases) has been implicated in acid extrusion and invasiveness of some cancers, yet often on the basis of unspecific inhibitors. Serving as a membrane anchor directing V-ATPase localization, the a subunit of the V0 domain of the V-ATPase (ATP6V0a1-4) is particularly interesting in this regard. Here, we map the regulation and roles of ATP6V0a3 in migration, invasion, and growth in pancreatic ductal adenocarcinoma (PDAC) cells. a3 mRNA and protein levels were upregulated in PDAC cell lines compared to non-cancer pancreatic epithelial cells. Under control conditions, a3 localization was mainly endo-/lysosomal, and its knockdown had no detectable effect on pHi regulation after acid loading. V-ATPase inhibition, but not a3 knockdown, increased HIF-1α expression and decreased proliferation and autophagic flux under both starved and non-starved conditions, and spheroid growth of PDAC cells was also unaffected by a3 knockdown. Strikingly, a3 knockdown increased migration and transwell invasion of Panc-1 and BxPC-3 PDAC cells, and increased gelatin degradation in BxPC-3 cells yet decreased it in Panc-1 cells. We conclude that in these PDAC cells, a3 is upregulated and negatively regulates migration and invasion, likely in part via effects on extracellular matrix degradation.

Emerging insights on the role of V‐ATPase in human diseases: Therapeutic challenges and opportunities

“…Besides its plasmalemmal localization, V‐ATPase is also overexpressed in different types of cancer cells 83,91,99–101 . Indeed, we showed that V‐ATPase is overexpressed in highly metastatic cancer cells derived from osteosarcoma, breast and prostate cancer, which is associated with higher extracellular acidification rate and more acidic lysosomes 82,102 .…”

Variation of Long Non-Coding RNA And mRNA Profiles in Breast Cancer Cells With Influences of Adipocytes

“…Besides, transcripts ENST00000524816.7 and ENST00000471245.1 were respectively noncoding regions of gene TRIM29 and CKS1B, which were responsible for breast cancer proliferation, metastasis and invasion (26,27). ENST00000587299.1 and ENST00000553238.5 participated in the transcription of gene SLC8B1 and ATP6V0A1 that was associated with the invasive process of oral tongue cancer and pancreatic ductal adenocarcinoma, respectively (28,29). Therefore, lncRNAs may be the vital ingredients in the process of adipocytes induced progression of breast cancer cells.…”

Proton Pump Inhibitors Reduce Pancreatic Adenocarcinoma Progression by Selectively Targeting H+, K+-ATPases in Pancreatic Cancer and Stellate Cells

“…It is widely believed that at high concentrations PPIs in fact inhibit the vacuolar V-ATPase, and older studies nicely show that these pumps do indeed require much higher concentrations of PPIs compared to H + ,K + -ATPases [33,34]. V-ATPases are highly expressed in many cancers, including PDAC [35,36]. In mammalian cells, the most important cellular site for V-ATPase is in endocytotic and secretory granules.…”

“…In certain specialized cells performing significant acid/base transport, e.g., renal intercalated cells, epididymal cells, osteoclasts and phagocytes, V-ATPase also localizes to the plasma membrane [37]. Additionally, one study shows that in MCF-7 cancer cells the pump re-localizes from lysosomes to the plasma membrane following lysosomal exocytosis [38], but this does not seem to be the case in PDAC [36].…”