Abstract 19827: The Stk25 Kinase Promotes Cell Survival and Metabolism in Cardiac Progenitor Cells
Rationale and Objective: c-Kit positive cardiac progenitor cells (CPC’s) have the capacity for expansion ex vivo and promote cardiac repair when applied therapeutically. They also provide a means for studying signaling pathways in tissue culture that has the potential for translation to overall cardiac physiology. Little is known about their internal kinase pathways that may be crucial for improving their growth and survival. We hypothesize that important kinase pathways can be identified through an agnostic high throughput knockdown screen and that modulation of these pathways can alter CPC physiology.
Methods and Results: Two separate primary CPC cell lines were derived from heart tissue discarded during left ventricular assist device implantation using magnetic cell sorting and characterized by flow cytometry for evidence of both c-Kit and cardiac lineage expression. Using cell proliferation as an output, a high throughput whole kinome screen was performed using a shRNA library. The kinase STK25 was identified in both lines as the top target for growth modulation. STK25 has no known substrates or known regulation but it has genetically been implicated in glucose and lipid metabolism as well as diabetes. Overexpression of STK25 in CPC’s resulted in increased growth and proliferation in both the fed and starved state as well as increased signaling through both AMPK and AKT kinase pathways. Knockdown of STK25 as well as CRISPR-Cas9 mediated knockout of STK25 in CPC’s resulted in diminished growth, proliferation and signaling through both AMPK and AKT signaling axes. Using an assay which measures glycolytic flux and mitochondrial respiration, overexpression of STK25 resulted in increased mitochondrial respiration and ATP production while knockdown led to diminished mitochondrial respiration. AMPK specific modulators were able to complement STK25’s effect on cell growth, proliferation and metabolism. In whole myocardial tissue samples, STK25 expression was increased both at the protein and the RNA level in heart failure when compared to normal hearts. This expression mirrored changes in the phosphorylation status of AMPK.
Conclusion: STK25 is a novel regulator of CPC growth, proliferation and metabolism and functions through the AMPK pathway.
Author Disclosures: B. Fine: None. Y. Shih: None. P. Colombo: None. G. Vunjak-Novakovic: None.
- © 2016 by American Heart Association, Inc.