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AKAP7 and Calcineurin Control CaM Kinases and Cell Growth
Author(s) -
Papenfuse Lael,
McFarland Hannah M,
DodgeKafka Kimberly,
Schmitt John M
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.644.11
Subject(s) - ionomycin , kinase , microbiology and biotechnology , mapk/erk pathway , calcineurin , chemistry , cell growth , signal transduction , cancer cell , biology , biochemistry , intracellular , medicine , cancer , transplantation , genetics
Estrogen (E2) and the agonist ionomycin elevate intracellular calcium and activate the calcium/calmodulin‐dependent protein kinases (CaM Kinases) in breast cancer cells. CaM Kinases regulate ERK leading to transcription and cell growth. Inhibition of CaM KK blocks breast cancer cell growth and protein phosphatases such as Calcineurin (CN) may negatively regulate CaM KK pathways. CN regulates CaM Kinases and associates with A‐kinase‐anchoring‐proteins (AKAPs). AKAPs are used to link together and regulate enzymes within in a signaling pathway. One specific AKAP, AKAP7, is involved in calcium signaling and may regulate CaM Kinase control of ERK activation in cancer cells. Our goal was to determine if CN and AKAP7 associated in breast cancer cells, and to examine the role of CN in regulating E2 and calcium activation of CaM KK/KI, ERK and cell growth in MCF‐7 and MDA‐MB‐231 cells. Our results suggest that E2 treatment of MCF‐7 cells activates CaM KI and ERK, an effect that is blocked by the selective CaM KK‐inhibitor STO‐609. Immunoprecipitation with purified STag‐AKAP7 but not STag‐AKAP5 revealed CaM KK and CaM KI association from E2‐treated MCF‐7 extracts. Interestingly, purified AKAP7 directly binds purified CaM KK and endogenous AKAP7 co‐localizes with CaM KK in MCF‐7 and MDA‐MB‐231 cells. Ionomycin stimulation of MCF‐7 cells also increased CaM KI and ERK activation an effect that was enhanced by treating cells with the CN inhibitor cyclosporin A (CsA). Similarly, ionomycin treatment enhanced the binding of endogenous CaM KK‐AKAP7‐CN as determined by both immunoprecipitation and confocal microscopy. Interestingly, siRNA knockdown of AKAP7 disrupted CaM KK association with CN and increased basal ERK phosphorylation in MCF‐7 cells. Finally, E2‐stimulated cell growth was inhibited by pre‐treatment with STO‐609 but not the CN inhibitor CsA. Taken together, these results suggest that AKAP7 directly associates with CaM KK/KI and forms a complex with CN that may function to negatively regulate CaM KK and CaM KI activation of ERK and cell growth. Support or Funding Information The Paul K. and Evalyn E. C. Richter Memorial Fund. This work was supported through a Life Science grant from the M.J. Murdock Charitable Trust to J.M.S. grant #2011267.