AMPK attenuates microtubule proliferation in cardiac hypertrophy

Abstract

Cell hypertrophy requires increased protein synthesis and expansion of the cytoskeletal networks that support cell enlargement. AMPK limits anabolic processes, such as protein synthesis, when energy supply is insufficient, but its role in cytoskeletal remodeling is not known. Here, we examined the influence of AMPK in cytoskeletal remodeling during cardiomyocyte hypertrophy, a clinically relevant condition in which cardiomyocytes enlarge but do not divide. In neonatal cardiomyocytes, activation of AMPK with 5-aminoimidazole carboxamide ribonucleotide (AICAR) or expression of constitutively active AMPK (CA-AMPK) attenuated cell area increase by hypertrophic stimuli (phenylephrine). AMPK activation had little effect on intermediate filaments or myofilaments but dramatically reduced microtubule stability, as measured by detyrosinated tubulin levels and cytoskeletal tubulin accumulation. Importantly, low-level AMPK activation limited cell expansion and microtubule growth independent of mTORC1 or protein synthesis repression, identifying a new mechanism by which AMPK regulates cell growth. Mechanistically, AICAR treatment increased Ser-915 phosphorylation of microtubule-associated protein 4 (MAP4), which reduces affinity for tubulin and prevents stabilization of microtubules (MTs). RNAi knockdown of MAP4 confirmed its critical role in cardiomyocyte MT stabilization. In support of a pathophysiological role for AMPK regulation of cardiac microtubules, AMPK α2 KO mice exposed to pressure overload (transverse aortic constriction; TAC) demonstrated reduced MAP4 phosphorylation and increased microtubule accumulation that correlated with the severity of contractile dysfunction. Together, our data identify the microtubule cytoskeleton as a sensitive target of AMPK activity, and the data suggest a novel role for AMPK in limiting accumulation and densification of microtubules that occurs in response to hypertrophic stress.

Decreased KCNE2 Expression Participates in the Development of Cardiac Hypertrophy by Regulation of Calcineurin–NFAT (Nuclear Factor of Activated T Cells) and Mitogen-Activated Protein Kinase Pathways

“…24,25 We thus examined the effect of KCNE2 knockdown on AMPactivated protein kinase phosphorylation. The result shows that the phosphorylated AMP-activated protein kinase was unaffected by KCNE2 knockdown ( Figure III in the Data Supplement), indicating that the activation of calcineurin-NFAT pathway is unrelated to AMP-activated protein kinase activation.…”

AMP kinase (PRKAA1)

“…Additionally, it is known that cardiac hypertrophy requires functional protein synthesis and expansion of the cellular cytoskeleton 77. Knockout of the AMPK α2 catalytic subunit in a mouse model exacerbated cardiac hypertrophy and heart failure in response to pressure overload, and this was associated with upregulated mTORC1 signalling 78.…”

“…Furthermore, a recent study has demonstrated that the microtubule cytoskeleton of cardiomyocytes is a sensitive target of AMPK 77. In fact, AMPK activation in neonatal cardiomyocytes markedly reduced microtubule stability 77.…”

Odanacatib Inhibits Resistin-induced Hypertrophic H9c2 Cardiomyoblast Cells Through LKB1/AMPK Pathway

“…Many studies show that AMPK is closely related to cardiac hypertrophy. The activity of AMPK is significantly decreased in hypertrophic cardiac myocytes, and AMPK can limit the protein synthesis and the remodeling of the cytoskeleton, which can inhibit cardiac hypertrophy 28 . EGCG prevents phenylephrine-induced myocardial hypertrophy through activating AMPK signaling pathway 29 .…”