The Vacuolar ATPase a2-subunit regulates Notch signaling in triple-negative breast cancer cells
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Sahithi Pamarthy1, Mukesh K. Jaiswal1, Arpita Kulshreshtha1, Gajendra K. Katara1, Alice Gilman-Sachs1, Kenneth D. Beaman1
1Department of Microbiology and Immunology, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA
Kenneth D. Beaman, e-mail: email@example.com
Keywords: a2V-ATPase, notch signaling, triple negative breast cancer, autophagy, bafilomycin
Received: May 06, 2015 Accepted: September 07, 2015 Published: September 18, 2015
Triple Negative Breast Cancer (TNBC) is a subtype of breast cancer with poor prognosis for which no targeted therapies are currently available. Notch signaling has been implicated in breast cancer but the factors that control Notch in TNBC are unknown. Because the Vacuolar ATPase has been shown to be important in breast cancer invasiveness, we investigated the role of a2-subunit isoform of Vacuolar ATPase (a2V) in regulating Notch signaling in TNBC. Confocal microscopy revealed that among all the ‘a’ subunit isoforms, a2V was uniquely expressed on the plasma membrane of breast cancer cells. Both a2V and NOTCH1 were elevated in TNBC tumors tissues and cell lines. a2V knockdown by siRNA as well as V-ATPase inhibition by Bafilomycin A1 (Baf A1) in TNBC cell lines enhanced Notch signaling by increasing the expression of Notch1 intracellular Domain (N1ICD). V-ATPase inhibition blocked NICD degradation by disrupting autophagy and lysosomal acidification as demonstrated by accumulation of LC3B and diminished expression of LAMP1 respectively. Importantly, treatment with Baf A1 or anti-a2V, a novel-neutralizing antibody against a2V hindered cell migration of TNBC cells. Our findings indicate that a2V regulates Notch signaling through its role in endolysosomal acidification and emerges as a potential target for TNBC.
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