Proton Channels are Present in Cell Membranes of the Breast Cancer Cell Line MDA MB 231 and Affect Recovery from an Acid Load

Abstract

Voltage gated proton channels (HV1) have been implicated in late stage breast cancer (Wang et al, 2012. J. Biol. Chem. 287:13877), where HV1 expression correlated with tumor size and poor prognosis. HV1 knockdown reduced cell proliferation and migration as well as matrix metalloprotease release. However, the presence of functional HV1 on cancer cell membranes has not been demonstrated and the mechanism by which they affect the function of these cells has not been elucidated.Here we show the definitive presence of functional HV1 on the membranes of MDA MB 231 cells, a highly metastatic triple negative cell line. We performed patch clamp experiments on these cells and were able to detect bona fide voltage- and pH-gated channels that were perfectly selective for protons. The membrane density of the channels in these cells was recorded as 3.5 pA/pF which is roughly 5-fold lower than the 15 pA/pF displayed in neutrophils. In order to show that HV1 expresses at a level sufficient to impact pH regulation within these cells, we acid loaded them using the ammonium prepulse technique and monitored pHi recovery utilizing SEER with SNARF-1. Inhibiting HV1 with 1 mM Zn2+ slowed recovery from an acid load by 3-fold, demonstrating that the expression of HV1 on these cells affects pH regulation in these cells.We conclude that one mechanism by which HV1 may influence the pathophysiology of breast cancer is by improving the ability of breast cancer cells to regulate their internal pH.Supported by the Bears Care and the Brian Piccolo fund.