Abstract 13968: AMPK Regulates Cardiac Looping by Phosphorylating CLIP-170 that Determines the Directional Cell Migration and Polarity
Introduction: AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism not only in metabolic organs but also in the heart as evidenced by AMPK gene-modified mice. However, the downstream targets of AMPK that regulates physiological function in the heart have not been fully identified.
Methods and Results: To identify a novel AMPK substrate, we performed unique two-step column chromatography. We identified a novel AMPK substrate; cytoplasmic linker protein of 170 KDa (CLIP-170). CLIP-170 is one of the microtubule plus-end proteins regulating microtubule dynamics. AMPK phosphorylates Ser 311 of CLIP-170 both in vitro and in vivo. Inhibition of AMPK or expression of a non-phosphorylatable CLIP-170 mutant in cultured cells resulted in prolonged and increased accumulation of CLIP-170 at microtubule plus ends and slower tubulin polymerization/depolymerization. The failure of microtubule dynamics caused by the defect of CLIP-170 phosphorylation by AMPK led to stabilization of microtubules and perturbed cell migration. All of these phenotypes were rescued by expression of a phosphomimetic CLIP-170 mutant, supporting the importance of CLIP-170 phosphorylation by AMPK. Consistently, in vivo, zebrafish specifically expressing non-phosphorylatable CLIP-170 in heart showed abnormal heart looping without the commitment of cardiac precursor cell to cardiomyocytes, indicating the essential role of AMPK for cardiomyocyte migration.
Conclusions: AMPK controls basic cellular functions by regulating microtubule dynamics through CLIP-170 phosphorylation. This newly identified signalling pathway determines the cellular and tissue polarity in the heart.
- © 2010 by American Heart Association, Inc.