Michael S. Kapiloff, MD, PhD

All Publications

• cAMP At Perinuclear mAKAPalpha Signalosomes Is Regulated By Local Ca2+ Signaling In Primary Hippocampal Neurons. eNeuro Boczek, T., Yu, Q., Zhu, Y., Dodge-Kafka, K. L., Goldberg, J. L., Kapiloff, M. S. 2021

  Abstract

  The second messenger cyclic adenosine monophosphate (cAMP) is important for the regulation of neuronal structure and function, including neurite extension. A perinuclear cAMP compartment organized by the scaffold protein muscle A-Kinase Anchoring Protein alpha (mAKAPalpha/AKAP6alpha) is sufficient and necessary for axon growth by rat hippocampal neurons in vitro Here, we report that cAMP at mAKAPalpha signalosomes is regulated by local Ca2+ signaling that mediates activity-dependent cAMP elevation within that compartment. Simultaneous Forster resonance energy transfer (FRET) imaging using the PKA activity reporter AKAR4 and intensiometric imaging using the RCaMP1h fluorescent Ca2+ sensor revealed that membrane depolarization by KCl selectively induced activation of perinuclear PKA activity. Activity-dependent perinuclear PKA activity was dependent upon expression of the mAKAPalpha scaffold, while both perinuclear Ca2+ elevation and PKA activation were dependent upon voltage-dependent L-type Ca2+ channel activity. Importantly, chelation of Ca2+ by a nuclear envelope-localized parvalbumin fusion protein inhibited both activity-induced perinuclear PKA activity and axon elongation. Together, this study provides evidence for a model in which a neuronal perinuclear cAMP compartment is locally regulated by activity-dependent Ca2+ influx, providing local control for the enhancement of neurite extension.Significance statement cAMP-dependent signaling has been implicated as a positive regulator of neurite outgrowth and axon regeneration. However, the mechanisms regulating cAMP signaling relevant to these processes remain largely unknown. Live cell imaging techniques are used to study the regulation by local Ca2+ signals of an mAKAPalpha-associated cAMP compartment at the neuronal nuclear envelope, providing new mechanistic insight into CNS neuronal signaling transduction conferring axon outgrowth.

  View details for DOI 10.1523/ENEURO.0298-20.2021

  View details for PubMedID 33495246

• Calcineurin Abeta-Specific Anchoring Confers Isoform-Specific Compartmentation and Function in Pathological Cardiac Myocyte Hypertrophy. Circulation Li, X., Li, J., Martinez, E. C., Froese, A., Passariello, C. L., Henshaw, K., Rusconi, F., Li, Y., Yu, Q., Thakur, H., Nikolaev, V. O., Kapiloff, M. S. 2020

  Abstract

  Background: The Ca2+/calmodulin-dependent phosphatase calcineurin is a key regulator of cardiac myocyte hypertrophy in disease. An unexplained paradox is how the Abeta isoform of calcineurin (CaNAbeta) is required for induction of pathological myocyte hypertrophy, despite calcineurin Aalpha expression in the same cells. In addition, it is unclear how the pleiotropic second messenger Ca2+ drives excitation-contraction coupling, while not stimulating hypertrophy via calcineurin in the normal heart. Elucidation of the mechanisms conferring this selectively in calcineurin signaling should reveal new strategies for targeting the phosphatase in disease. Methods: Primary adult rat ventricular myocytes were studied for morphology and intracellular signaling. New Forster Resonance Energy Transfer (FRET) reporters were used to assay Ca2+ and calcineurin activity in living cells. Conditional gene deletion and adeno-associated virus (AAV)-mediated gene delivery in the mouse were used to study calcineurin signaling following transverse aortic constriction in vivo. Results: Cdc42-interacting protein (CIP4/TRIP10) was identified as a new polyproline domain-dependent scaffold for CaNAbeta2 by yeast-2-hybrid screen. Cardiac myocyte-specific CIP4 gene deletion in mice attenuated pressure overload-induced pathological cardiac remodeling and heart failure. Accordingly, blockade of CaNAbeta polyproline-dependent anchoring using a competing peptide inhibited concentric hypertrophy in cultured myocytes, while disruption of anchoring in vivo using an AAV gene therapy vector inhibited cardiac hypertrophy and improved systolic function after pressure overload. Live cell FRET biosensor imaging of cultured myocytes revealed that Ca2+ levels and calcineurin activity associated with the CIP4 compartment were increased by neurohormonal stimulation, but minimally by pacing. Conversely, Ca2+ levels and calcineurin activity detected by non-localized FRET sensors were induced by pacing and minimally by neurohormonal stimulation, providing functional evidence for differential intracellular compartmentation of Ca2+ and calcineurin signal transduction. Conclusions: These results support a structural model for Ca2+ and CaNAbeta compartmentation in cells based upon an isoform-specific mechanism for calcineurin protein-protein interaction and localization. This mechanism provides an explanation for the specific role of CaNAbeta in hypertrophy and its selective activation under conditions of pathologic stress. Disruption of CaNAbeta polyproline-dependent anchoring constitutes a rational strategy for therapeutic targeting of CaNAbeta-specific signaling responsible for pathological cardiac remodeling in cardiovascular disease deserving of further pre-clinical investigation.

  View details for DOI 10.1161/CIRCULATIONAHA.119.044893

  View details for PubMedID 32611257

• Calcineurin-AKAP interactions: therapeutic targeting of a pleiotropic enzyme with a little help from its friends JOURNAL OF PHYSIOLOGY-LONDON Gildart, M., Kapiloff, M. S., Dodge-Kafka, K. L. 2020; 598 (14): 3029–42

  Abstract

  The ubiquitous Ca2+ /calmodulin-dependent phosphatase calcineurin is a key regulator of pathological cardiac hypertrophy whose therapeutic targeting in heart disease has been elusive due to its role in other essential biological processes. Calcineurin is targeted to diverse intracellular compartments by association with scaffold proteins, including by multivalent A-kinase anchoring proteins (AKAPs) that bind protein kinase A and other important signalling enzymes determining cardiac myocyte function and phenotype. Calcineurin anchoring by AKAPs confers specificity to calcineurin function in the cardiac myocyte. Targeting of calcineurin 'signalosomes' may provide a rationale for inhibiting the phosphatase in disease.

  View details for DOI 10.1113/JP276756

  View details for Web of Science ID 000548282400015

  View details for PubMedID 30488951

• Optic Nerve Crush in Mice to Study Retinal Ganglion Cell Survival and Regeneration. Bio-protocol Cameron, E. G., Xia, X., Galvao, J., Ashouri, M., Kapiloff, M. S., Goldberg, J. L. 2020; 10 (6)

  Abstract

  In diseases such as glaucoma, the failure of retinal ganglion cell (RGC) neurons to survive or regenerate their optic nerve axons underlies partial and, in some cases, complete vision loss. Optic nerve crush (ONC) serves as a useful model not only of traumatic optic neuropathy but also of glaucomatous injury, as it similarly induces RGC cell death and degeneration. Intravitreal injection of adeno-associated virus serotype 2 (AAV2) has been shown to specifically and efficiently transduce RGCs in vivo and has thus been proposed as an effective means of gene delivery for the treatment of glaucoma. Indeed, we and others routinely use AAV2 to study the mechanisms that promote neuroprotection and axon regeneration in RGCs following ONC. Herein, we describe a step-by-step protocol to assay RGC survival and regeneration in mice following AAV2-mediated transduction and ONC injury including 1) intravitreal injection of AAV2 viral vectors, 2) optic nerve crush, 3) cholera-toxin B (CTB) labeling of regenerating axons, 4) optic nerve clearing, 5) flat mount retina immunostaining, and 6) quantification of RGC survival and regeneration. In addition to providing all the materials and procedural details necessary to execute this protocol, we highlight its advantages over other similar published approaches and include useful tips to ensure its faithful reproduction in any modern laboratory.

  View details for DOI 10.21769/BioProtoc.3559

  View details for PubMedID 32368566

• Compartmentalization of local cAMP signaling in neuronal growth and survival NEURAL REGENERATION RESEARCH Boczek, T., Kapiloff, M. 2020; 15 (3): 453–54

  View details for DOI 10.4103/1673-5374.266055

  View details for Web of Science ID 000507627400012

  View details for PubMedID 31571655

  View details for PubMedCentralID PMC6921356

• MEF2 transcription factors differentially contribute to retinal ganglion cell loss after optic nerve injury. PloS one Xia, X., Yu, C. Y., Bian, M., Sun, C. B., Tanasa, B., Chang, K. C., Bruffett, D. M., Thakur, H., Shah, S. H., Knasel, C., Cameron, E. G., Kapiloff, M. S., Goldberg, J. L. 2020; 15 (12): e0242884

  Abstract

  Loss of retinal ganglion cells (RGCs) in optic neuropathies results in permanent partial or complete blindness. Myocyte enhancer factor 2 (MEF2) transcription factors have been shown to play a pivotal role in neuronal systems, and in particular MEF2A knockout was shown to enhance RGC survival after optic nerve crush injury. Here we expanded these prior data to study bi-allelic, tri-allelic and heterozygous allele deletion. We observed that deletion of all MEF2A, MEF2C, and MEF2D alleles had no effect on RGC survival during development. Our extended experiments suggest that the majority of the neuroprotective effect was conferred by complete deletion of MEF2A but that MEF2D knockout, although not sufficient to increase RGC survival on its own, increased the positive effect of MEF2A knockout. Conversely, MEF2A over-expression in wildtype mice worsened RGC survival after optic nerve crush. Interestingly, MEF2 transcription factors are regulated by post-translational modification, including by calcineurin-catalyzed dephosphorylation of MEF2A Ser-408 known to increase MEF2A-dependent transactivation in neurons. However, neither phospho-mimetic nor phospho-ablative mutation of MEF2A Ser-408 affected the ability of MEF2A to promote RGC death in vivo after optic nerve injury. Together these findings demonstrate that MEF2 gene expression opposes RGC survival following axon injury in a complex hierarchy, and further support the hypothesis that loss of or interference with MEF2A expression might be beneficial for RGC neuroprotection in diseases such as glaucoma and other optic neuropathies.

  View details for DOI 10.1371/journal.pone.0242884

  View details for PubMedID 33315889

• Signalosome-Regulated SRF Phosphorylation Determining Myocyte Growth in Width versus Length as a Therapeutic Target for Heart Failure. Circulation Li, J., Tan, Y., Passariello, C. L., Martinez, E. C., Kritzer, M. D., Li, X., Li, X., Li, Y., Yu, Q., Ohgi, K., Thakur, H., MacArthur, J. W., Ivey, J. R., Woo, Y. J., Emter, C. A., Dodge-Kafka, K., Rosenfeld, M. G., Kapiloff, M. S. 2020

  Abstract

  Background: Concentric and eccentric cardiac hypertrophy are associated with pressure and volume overload, respectively, in cardiovascular disease both conferring an increased risk of heart failure. These contrasting forms of hypertrophy are characterized by asymmetric growth of the cardiac myocyte in mainly width or length, respectively. The molecular mechanisms determining myocyte preferential growth in width versus length remain poorly understood. Identification of the mechanisms governing asymmetric myocyte growth could provide new therapeutic targets for the prevention or treatment of heart failure. Methods: Primary adult rat ventricular myocytes, adeno-associated virus (AAV)-mediated gene delivery in mice, and human tissue samples are used to define a regulatory pathway controlling pathological myocyte hypertrophy. Chromatin Immunoprecipitation Assays with Sequencing (ChIP-seq) and Precision Nuclear Run-On Sequencing (PRO-seq) are used to define a transcriptional mechanism. Results: Here we report that asymmetric cardiac myocyte hypertrophy is modulated by serum response factor (SRF) phosphorylation, constituting an epigenomic switch balancing the growth in width versus length of adult ventricular myocytes in vitro and in vivo. SRF Ser103 phosphorylation is bidirectionally regulated by p90 ribosomal S6 kinase type 3 (RSK3) and protein phosphatase 2A (PP2A) at signalosomes organized by the scaffold protein muscle A-kinase anchoring protein β (mAKAPβ), such that increased SRF phosphorylation activates Activator Protein 1 (AP1)-dependent enhancers that direct myocyte growth in width. AAV are used to express in vivo mAKAPβ-derived RSK3 and PP2A anchoring disruptor peptides that block the association of the enzymes with the mAKAPβ scaffold. Inhibition of RSK3 signaling prevents concentric cardiac remodeling due to pressure overload, while inhibition of PP2A signaling prevents eccentric cardiac remodeling induced by myocardial infarction, in each case improving cardiac function. SRF Ser103 phosphorylation is significantly decreased in dilated human hearts, supporting the notion that modulation of the mAKAPβ-SRF signalosome could be a new therapeutic approach for human heart failure. Conclusions: We have identified a new molecular switch, namely mAKAPβ signalosome-regulated SRF phosphorylation, that controls a transcriptional program responsible for modulating changes in cardiac myocyte morphology that occur secondary to pathological stressors. Complementary AAV-based gene therapies constitute rationally-designed strategies for a new translational modality for heart failure.

  View details for DOI 10.1161/CIRCULATIONAHA.119.044805

  View details for PubMedID 32933333

• A Novel Recessive Mutation in SPEG Causes Early Onset Dilated Cardiomyopathy. PLoS genetics Levitas, A., Muhammad, E., Zhang, Y., Perea Gil, I., Serrano, R., Diaz, N., Arafat, M., Gavidia, A. A., Kapiloff, M. S., Mercola, M., Etzion, Y., Parvari, R., Karakikes, I. 2020; 16 (9): e1009000

  Abstract

  Dilated cardiomyopathy (DCM) is a common cause of heart failure and sudden cardiac death. It has been estimated that up to half of DCM cases are hereditary. Mutations in more than 50 genes, primarily autosomal dominant, have been reported. Although rare, recessive mutations are thought to contribute considerably to DCM, especially in young children. Here we identified a novel recessive mutation in the striated muscle enriched protein kinase (SPEG, p. E1680K) gene in a family with nonsyndromic, early onset DCM. To ascertain the pathogenicity of this mutation, we generated SPEG E1680K homozygous mutant human induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) using CRISPR/Cas9-mediated genome editing. Functional studies in mutant iPSC-CMs showed aberrant calcium homeostasis, impaired contractility, and sarcomeric disorganization, recapitulating the hallmarks of DCM. By combining genetic analysis with human iPSCs, genome editing, and functional assays, we identified SPEG E1680K as a novel mutation associated with early onset DCM and provide evidence for its pathogenicity in vitro. Our study provides a conceptual paradigm for establishing genotype-phenotype associations in DCM with autosomal recessive inheritance.

  View details for DOI 10.1371/journal.pgen.1009000

  View details for PubMedID 32925938

• AKAP6 orchestrates the nuclear envelope microtubule-organizing center by linking golgi and nucleus via AKAP9. eLife Vergarajauregui, S., Becker, R., Steffen, U., Sharkova, M., Esser, T., Petzold, J., Billing, F., Kapiloff, M. S., Schett, G., Thievessen, I., Engel, F. B. 2020; 9

  Abstract

  The switch from centrosomal microtubule-organizing centers (MTOCs) to non-centrosomal MTOCs during differentiation is poorly understood. Here, we identify AKAP6 as key component of the nuclear envelope MTOC. In rat cardiomyocytes, AKAP6 anchors centrosomal proteins to the nuclear envelope through its spectrin repeats, acting as an adaptor between nesprin-1alpha and Pcnt or AKAP9. In addition, AKAP6 and AKAP9 form a protein platform tethering the Golgi to the nucleus. Both Golgi and nuclear envelope exhibit MTOC activity utilizing either AKAP9, or Pcnt-AKAP9, respectively. AKAP6 is also required for formation and activity of the nuclear envelope MTOC in human osteoclasts. Moreover, ectopic expression of AKAP6 in epithelial cells is sufficient to recruit endogenous centrosomal proteins. Finally, AKAP6 is required for cardiomyocyte hypertrophy and osteoclast bone resorption activity. Collectively, we decipher the MTOC at the nuclear envelope as a bi-layered structure generating two pools of microtubules with AKAP6 as a key organizer.

  View details for DOI 10.7554/eLife.61669

  View details for PubMedID 33295871

• mAKAP beta signalosomes - A nodal regulator of gene transcription associated with pathological cardiac remodeling CELLULAR SIGNALLING Dodge-Kafka, K., Gildart, M., Tokarski, K., Kapiloff, M. S. 2019; 63: 109357

  Abstract

  Striated myocytes compose about half of the cells of the heart, while contributing the majority of the heart's mass and volume. In response to increased demands for pumping power, including in diseases of pressure and volume overload, the contractile myocytes undergo non-mitotic growth, resulting in increased heart mass, i.e. cardiac hypertrophy. Myocyte hypertrophy is induced by a change in the gene expression program driven by the altered activity of transcription factors and co-repressor and co-activator chromatin-associated proteins. These gene regulatory proteins are subject to diverse post-translational modifications and serve as nuclear effectors for intracellular signal transduction pathways, including those controlled by cyclic nucleotides and calcium ion. Scaffold proteins contribute to the underlying architecture of intracellular signaling networks by targeting signaling enzymes to discrete intracellular compartments, providing specificity to the regulation of downstream effectors, including those regulating gene expression. Muscle A-kinase anchoring protein β (mAKAPβ) is a well-characterized scaffold protein that contributes to the regulation of pathological cardiac hypertrophy. In this review, we discuss the mechanisms how this prototypical scaffold protein organizes signalosomes responsible for the regulation of class IIa histone deacetylases and cardiac transcription factors such as NFAT, MEF2, and HIF-1α, as well as how this signalosome represents a novel therapeutic target for the prevention or treatment of heart failure.

  View details for DOI 10.1016/j.cellsig.2019.109357

  View details for Web of Science ID 000487173000001

  View details for PubMedID 31299211

  View details for PubMedCentralID PMC7197268

• Regulation of Neuronal Survival and Axon Growth by a Perinuclear cAMP Compartment JOURNAL OF NEUROSCIENCE Boczek, T., Cameron, E. G., Yu, W., Xia, X., Shah, S. H., Chabeco, B., Galvao, J., Nahmou, M., Li, J., Thakur, H., Goldberg, J. L., Kapiloff, M. S. 2019; 39 (28): 5466–80

  View details for DOI 10.1523/JNEUROSCI.2752-18.2019

  View details for Web of Science ID 000474719500005

• Muscle A-kinase-anchoring protein-beta-bound calcineurin toggles active and repressive transcriptional complexes of myocyte enhancer factor 2D JOURNAL OF BIOLOGICAL CHEMISTRY Li, J., Paris, S., Thakur, H., Kapiloff, M. S., Dodge-Kafka, K. L. 2019; 294 (7): 2543–54

  View details for DOI 10.1074/jbc.RA118.005465

  View details for Web of Science ID 000458895400028

• Bidirectional regulation of HDAC5 by mAKAP beta signalosomes in cardiac myocytes JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY Dodge-Kafka, K. L., Gildart, M., Li, J., Thakur, H., Kapiloff, M. S. 2018; 118: 13–25

  Abstract

  Class IIa histone deacetylases (HDACs) are transcriptional repressors whose nuclear export in the cardiac myocyte is associated with the induction of pathological gene expression and cardiac remodeling. Class IIa HDACs are regulated by multiple, functionally opposing post-translational modifications, including phosphorylation by protein kinase D (PKD) that promotes nuclear export and phosphorylation by protein kinase A (PKA) that promotes nuclear import. We have previously shown that the scaffold protein muscle A-kinase anchoring protein β (mAKAPβ) orchestrates signaling in the cardiac myocyte required for pathological cardiac remodeling, including serving as a scaffold for both PKD and PKA. We now show that mAKAPβ is a scaffold for HDAC5 in cardiac myocytes, forming signalosomes containing HDAC5, PKD, and PKA. Inhibition of mAKAPβ expression attenuated the phosphorylation of HDAC5 by PKD and PKA in response to α- and β-adrenergic receptor stimulation, respectively. Importantly, disruption of mAKAPβ-HDAC5 anchoring prevented the induction of HDAC5 nuclear export by α-adrenergic receptor signaling and PKD phosphorylation. In addition, disruption of mAKAPβ-PKA anchoring prevented the inhibition by β-adrenergic receptor stimulation of α-adrenergic-induced HDAC5 nuclear export. Together, these data establish that mAKAPβ signalosomes serve to bidirectionally regulate the nuclear-cytoplasmic localization of class IIa HDACs. Thus, the mAKAPβ scaffold serves as a node in the myocyte regulatory network controlling both the repression and activation of pathological gene expression in health and disease, respectively.

  View details for PubMedID 29522762

  View details for PubMedCentralID PMC5940533

• Intracellular compartmentation of cAMP promotes neuroprotection and regeneration of CNS neurons. Neural regeneration research Cameron, E. G., Kapiloff, M. S. 2017; 12 (2): 201–2

  View details for PubMedID 28400794

  View details for PubMedCentralID PMC5361496