Effects of Vacuolar H⁺‐ATPase Inhibition on Activation of Cathepsin B and Cathepsin L Secreted from MDA‐MB231 Breast Cancer Cells

Abstract

Studies indicate secreted cathepsins are involved in metastasis. V‐ATPases, which are necessary for activating intracellular cathepsins, also play a role in metastasis and are targeted to the plasma membrane of metastatic breast cancer cells. We are interested in a connection between cell surface V‐ATPases, activation of secreted cathepsins and the metastatic phenotype of MDA‐MB231 cells. We investigated whether V‐ATPase inhibition would reduce the activity of secreted cathepsin B and cathepsin L. Using cell lysates and conditioned media, we measured cathepsin B and L activity within and outside of the cells. We found different forms of cathepsin B and L were secreted representing the pre‐pro, pro and active forms of the proteases. Cathepsin B activity was higher than cathepsin L in conditioned media and in cell lysates. V‐ATPase inhibition by concanamycin A decreased cathepsin B activity in conditioned media and significantly decreased cathepsin B activity in cell lysates. Cathepsin L activity showed a slight decrease in cell lysates. Changes in the activity of secreted and intracellular cathepsins following V‐ATPase inhibition were supported by changes in the amounts of pro and active forms of cathepsins B in conditioned media and cathepsin B and L in cell lysates. Overall, our data shows that inactive forms of cathepsins B and L are secreted from the MB231 cells and V‐ATPase activity is important for the activation of secreted cathepsin B. This indicates a connection between cell surface V‐ATPases in metastatic breast cancer cells and the function of secreted cathepsin B.Support or Funding InformationDenison University Anderson Fellowship, Denison University Research FundThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.