A Kinase Interacting Protein 1 (AKIP1) promotes cardiomyocyte elongation and physiological cardiac remodelling

www.nature.com/scientificreports OPEN A Kinase Interacting Protein 1 (AKIP1) promotes cardiomyocyte elongation and physiological cardiac remodelling Kirsten T. Nijholt 1, Pablo I. Sánchez‑Aguilera 1, Harmen G. Booij 1, Silke U. Oberdorf‑Maass 1, Martin M. Dokter 1, Anouk H. G. Wolters 2, Ben N. G. Giepmans 2, Wiek H. van Gilst 1, Joan H. Brown 3, Rudolf A. de Boer 1, Herman H. W. Silljé 1 & B. Daan Westenbrink 1* A Kinase Interacting Protein 1 (AKIP1) is a signalling adaptor that promotes physiological hypertrophy in vitro. The purpose of this study is to determine if AKIP1 promotes physiological cardiomyocyte hypertrophy in vivo. Therefore, adult male mice with cardiomyocyte-specific overexpression of AKIP1 (AKIP1-TG) and wild type (WT) littermates were caged individually for four weeks in the presence or absence of a running wheel. Exercise performance, heart weight to tibia length (HW/TL), MRI, histology, and left ventricular (LV) molecular markers were evaluated. While exercise parameters were comparable between genotypes, exercise-induced cardiac hypertrophy was augmented in AKIP1-TG vs. WT mice as evidenced by an increase in HW/TL by weighing scale and in LV mass on MRI. AKIP1-induced hypertrophy was predominantly determined by an increase in cardiomyocyte length, which was associated with reductions in p90 ribosomal S6 kinase 3 (RSK3), increments of phosphatase 2A catalytic subunit (PP2Ac) and dephosphorylation of serum response factor (SRF). With electron microscopy, we detected clusters of AKIP1 protein in the cardiomyocyte nucleus, which can potentially influence signalosome formation and predispose a switch in transcription upon exercise. Mechanistically, AKIP1 promoted exercise-induced activation of protein kinase B (Akt), downregulation of CCAAT Enhancer Binding Protein Beta (C/EBPβ) and de-repression of Cbp/ p300 interacting transactivator with Glu/Asp rich carboxy-terminal domain 4 (CITED4). Concludingly, we identified AKIP1 as a novel regulator of cardiomyocyte elongation and physiological cardiac remodelling with activation of the RSK3-PP2Ac-SRF and Akt-C/EBPβ-CITED4 pathway. These findings suggest that AKIP1 may serve as a nodal point for physiological reprogramming of cardiac remodelling. The heart continuously adapts to fluctuations in metabolic demands of peripheral tissues1,2. In response to sustained or repetitive increases in workload such as exercise or pressure overload, the heart responds by increasing muscle mass, a process known as cardiac h ypertrophy1. The increase in muscle mass provides mechanical advantages as it reduces ventricular wall stress and increases contractile performance1,3. Although cardiac hypertrophy provides early functional compensation, it can also be characterised by maladaptive changes in the histological, molecular, biochemical, and metabolic composition of the myocardium that can ultimately cause heart failure (HF)1,3,4. There are, however, important distinctions between cardiac hypertrophy that occur in response to physiological stimuli such as exercise and pregnancy and pathological stimuli such as pressure o verload1,2. Most importantly, physiological and pathological cardiac hypertrophy are governed by distinct signal transduction pathways with distinct histological, biochemical and molecular signatures. For instance, pathological cardiac hypertrophy is accompanied by a predominant increase in cardiomyocyte width, relative reductions in capillary density, re-expression of the foetal cardiac genes, mitochondrial dysfunction, and fi brosis1,3–5. In contrast, physiological cardiac hypertrophy induced by endurance exercise is characterized by a preferential increase in 1 Department of Cardiology, University Medical Centre Groningen, University of Groningen, P.O. Box 30.001, Hanzeplein 1, 9713 GZ, 9700 RB Groningen, The Netherlands. 2Department of Biomedical Sciences of Cells and Systems, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands. 3Department of Pharmacology, University of California San Diego, La Jolla, USA. *email: Scientific Reports | (2023) 13:4046 | https://doi.org/10.1038/s41598-023-30514-1 1 Vol.:(0123456789) www.nature.com/scientificreports/ cardiomyocyte length (eccentric hypertrophy), expansion of the capillary network and improvements in mitochondrial quantity and q uality1,2,4,6–8. While intense efforts have been devoted to the identification of pathways underlying pathological hypertrophy, relatively little is known about physiological hypertrophy. Identifying key factors regulating physiological cardiac hypertrophy should allow the design of therapies to shift pathological hypertrophy towards a more physiological end of the spectrum. An important distinction between physiological and pathological hypertrophy is that they are governed by distinct growth factors and signal transduction p athways1. Our group recently identified the signalling adaptor protein A Kinase Interacting Protein 1 (AKIP1) as a pro-hypertrophic gene9, the myocardial expression of which is increased in response to e xercise10 as well as in a transgenic mouse model of physiological h ypertrophy11. 12 In cultured cardiomyocytes, overexpression of AKIP1 improved mitochondrial function and induced a physiological type of hypertrophy through activation of the Akt-mTOR pathway13. Accordingly, we tested the hypothesis that cardiomyocyte-specific overexpression of AKIP1 in mice promotes cardiac hypertrophy in response to voluntary exercise in vivo. Methods Ethical approval. The Animal Ethics Committee from the University of Groningen approved the animal experiments (DEC6237F, 199105-01-005), which were performed following the protocols from Directive 2010/63/EU of the European Parliament. The study was reported in accordance with the recommendations of the ARRIVE guidelines. Animal model. A total of 44 adult male mice (8–12 weeks old) were included in the study population. This study population included mice with cardiomyocyte-specific overexpression of AKIP1 (AKIP1-TG) and their wild type (WT) littermates. AKIP1-TG mice were generated as described previously14. To validate whether there was AKIP1 overexpression in the heart of AKIP1-TG mice, mRNA and Western blot analysis was performed (Supplementary Fig. S1). Experimental model. AKIP1-TG mice and their WT littermates were caged individually in the presence or absence of a running wheel for four weeks. This resulted in two running groups (WT Run, AKIP1-TG Run) and two sedentary groups (WT Sed, AKIP1-TG Sed) (Fig. 1A). All mice had ad libitum access to food and water and were housed in 12:12 h dark–light cycles. Exercise performance. Exercise performance was recorded using a cyclometer connected to the running heel15. Mice that were housed with a running wheel in their individual cage, had a sensor and cyclometer w attached to the running wheel. The sensor on the running wheel automatically detected running activity as so (...truncated)