8.A.28 The Ankyrin (Ankyrin) Family Ankyrin-B (Ank2, ankyrin-2; 3924 aas) interacts directly with and is required for targeting and stability of the Na⁺/Ca²⁺ exchanger 1 in cardiomyocytes (Cunha et al., 2007). It is also required for assembly of the Na⁺,K⁺ ATPase and various membrane receptors and transporters (Liu et al., 2008). Exon organization and alternative splicing give rise to at least 30 ANK2 mRNA transcripts. The ANK2 gene consists of 53 exons spanning ~560 kbps (Cunha et al., 2008). Ankyrins are a family of adaptor proteins which associate with a group of structurally diverse ion channels and transporters including the Na/Ca exchanger (Li et al., 1993; Mohler et al., 2003; Mohler et al., 2005), the Na/K ATPase, voltage-gated Na⁺ channels, and the anion exchanger. Multiple lines of evidence predict a role for ankyrin polypeptides in the proper localization and stability of the Na/Ca exchanger at the cardiomyocyte plasma membrane. Ankyrin polypeptides directly bind to the cardiac Na/Ca exchanger with high affinity (Li et al., 1993; Mohler et al., 2005). Ankyrins have N-terminal Ank repeat units that are homologous to those of channel proteins in families 1.A.4 and 1.A.1. These repeats of about 100 residues, comprise of ankyrin B. They generally attach integral membrane proteins to cytoskeletal proteins. They are regulated by phosphorylation. Defects in Ank2 cause sick sinus syndrome with bradycardia (also called 'human sinus node dysfunction (SND)) (Le Scouarnec et al., 2008).
This family belongs to the Ankyrin Repeat Domain-containing (Ank) Superfamily.
References:
Cunha, S.R., N. Bhasin, and P.J. Mohler. (2007). Targeting and stability of Na/Ca Exchanger 1 in cardiomyocytes requires direct interaction with the membrane adaptor ankyrin-B. J. Biol. Chem. 282: 4875-4883.
Cunha, S.R., S. Le Scouarnec, J.J. Schott, and P.J. Mohler. (2008). Exon organization and novel alternative splicing of the human ANK2 gene: implications for cardiac function and human cardiac disease. J Mol. Cell Cardiol 45: 724-734.
Desmond, P.F., A. Labuza, J. Muriel, M.L. Markwardt, A.E. Mancini, M.A. Rizzo, and R.J. Bloch. (2017). Interactions between Small Ankyrin 1 and Sarcolipin Coordinately Regulate Activity of the Sarco(endo)plasmic Reticulum Ca²⁺-ATPase (SERCA1). J. Biol. Chem. [Epub: Ahead of Print]
Desmond, P.F., J. Muriel, M.L. Markwardt, M.A. Rizzo, and R.J. Bloch. (2015). Identification of Small Ankyrin 1 as a Novel Sarco(endo)plasmic Reticulum Ca²⁺-ATPase 1 (SERCA1) Regulatory Protein in Skeletal Muscle. J. Biol. Chem. 290: 27854-27867.
Dulhunty, A.F., L. Wei-LaPierre, M.G. Casarotto, and N.A. Beard. (2016). The Core Skeletal Muscle Ryanodine Receptor Calcium Release Complex. Clin Exp Pharmacol Physiol. [Epub: Ahead of Print]
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El-Dessouky, S.H., M.Y. Issa, M.M. Aboulghar, H.M. Gaafar, A.E. Elarab, M.I. Ateya, H.H. Omar, C. Beetz, and M.S. Zaki. (2020). Prenatal delineation of a distinct lethal fetal syndrome caused by a homozygous truncating KIDINS220 variant. Am J Med Genet A. [Epub: Ahead of Print]
Gergs, U., T. Berndt, J. Buskase, L.R. Jones, U. Kirchhefer, F.U. Müller, K.D. Schlüter, W. Schmitz, and J. Neumann. (2007). On the role of junctin in cardiac Ca²⁺ handling, contractility, and heart failure. Am. J. Physiol. Heart Circ Physiol 293: H728-734.
Goonasekera, S.A., N.A. Beard, L. Groom, T. Kimura, A.D. Lyfenko, A. Rosenfeld, I. Marty, A.F. Dulhunty, and R.T. Dirksen. (2007). Triadin binding to the C-terminal luminal loop of the ryanodine receptor is important for skeletal muscle excitation contraction coupling. J Gen Physiol 130: 365-378.
Jaudon, F., M. Albini, S. Ferroni, F. Benfenati, and F. Cesca. (2021). A developmental stage- and Kidins220-dependent switch in astrocyte responsiveness to brain-derived neurotrophic factor. J Cell Sci 134:.
Jaudon, F., M. Albini, S. Ferroni, F. Benfenati, and F. Cesca. (2021). A developmental stage- and Kidins220-dependent switch in astrocyte responsiveness to brain-derived neurotrophic factor. J Cell Sci. [Epub: Ahead of Print]
Le Scouarnec, S., N. Bhasin, C. Vieyres, T.J. Hund, S.R. Cunha, O. Koval, C. Marionneau, B. Chen, Y. Wu, S. Demolombe, L.S. Song, H. Le Marec, V. Probst, J.J. Schott, M.E. Anderson, and P.J. Mohler. (2008). Dysfunction in ankyrin-B-dependent ion channel and transporter targeting causes human sinus node disease. Proc. Natl. Acad. Sci. USA 105: 15617-15622.
Li, Z.P., E.P. Burke, J.S. Frank, V. Bennett, and K.D. Philipson. (1993). The cardiac Na⁺-Ca²⁺ exchanger binds to the cytoskeletal protein ankyrin. J. Biol. Chem. 268: 11489-11491.
Liao, Y.H., S.M. Hsu, and P.H. Huang. (2007). ARMS depletion facilitates UV irradiation induced apoptotic cell death in melanoma. Cancer Res 67: 11547-11556.
Liu, X., Z. Spicarová, S. Rydholm, J. Li, H. Brismar, and A. Aperia. (2008). Ankyrin B modulates the function of Na,K-ATPase/inositol 1,4,5-trisphosphate receptor signaling microdomain. J. Biol. Chem. 283: 11461-11468.
Lu, H., D.N. Rate, J.T. Song, and J.T. Greenberg. (2003). ACD6, a novel ankyrin protein, is a regulator and an effector of salicylic acid signaling in the Arabidopsis defense response. Plant Cell 15: 2408-2420.
Lu, H., S. Salimian, E. Gamelin, G. Wang, J. Fedorowski, W. LaCourse, and J.T. Greenberg. (2009). Genetic analysis of acd6-1 reveals complex defense networks and leads to identification of novel defense genes in Arabidopsis. Plant J. 58: 401-412.
Lu, H., Y. Liu, and J.T. Greenberg. (2005). Structure-function analysis of the plasma membrane- localized Arabidopsis defense component ACD6. Plant J. 44: 798-809.
Mack, K. and M.J.M. Fischer. (2017). Disrupting sensitization of TRPV4. Neuroscience 352: 1-8. [Epub: Ahead of Print]
Marty, I. (2015). Triadin regulation of the ryanodine receptor complex. J. Physiol. 593: 3261-3266.
Miura, K. and M. Ohta. (2010). SIZ1, a small ubiquitin-related modifier ligase, controls cold signaling through regulation of salicylic acid accumulation. J Plant Physiol. 167: 555-560.
Mohler, P.J., J.J. Schott, A.O. Gramolini, K.W. Dilly, S. Guatimosim, W.H. duBell, L.S. Song, K. Haurogne, F. Kyndt, M.E. Ali, T.B. Rogers, W.J. Lederer, D. Escande, H. Le Marec, and V. Bennett. (2003). Ankyrin-B mutation causes type 4 long-QT cardiac arrhythmia and sudden cardiac death. Nature 421: 634-639.
Mohler, P.J., J.Q. Davis, and V. Bennett. (2005). Ankyrin-B coordinates the Na/K ATPase, Na/Ca exchanger, and InsP3 receptor in a cardiac T-tubule/SR microdomain. PLoS Biol. 3: e423.
Monteiro, P. and G. Feng. (2017). SHANK proteins: roles at the synapse and in autism spectrum disorder. Nat Rev Neurosci 18: 147-157.
Rao, P.V. and R. Maddala. (2016). Ankyrin-B in lens architecture and biomechanics: Just not tethering but more. Bioarchitecture 6: 39-45.
Rossi, D., S. Lorenzini, E. Pierantozzi, F. Van Petegem, D. Osamwonuyi Amadsun, and V. Sorrentino. (2022). Multiple regions within junctin drive its interaction with calsequestrin-1 and its localization to triads in skeletal muscle. J Cell Sci 135:.
Roux-Buisson, N., M. Cacheux, A. Fourest-Lieuvin, J. Fauconnier, J. Brocard, I. Denjoy, P. Durand, P. Guicheney, F. Kyndt, A. Leenhardt, H. Le Marec, V. Lucet, P. Mabo, V. Probst, N. Monnier, P.F. Ray, E. Santoni, P. Trémeaux, A. Lacampagne, J. Fauré, J. Lunardi, and I. Marty. (2012). Absence of triadin, a protein of the calcium release complex, is responsible for cardiac arrhythmia with sudden death in human. Hum Mol Genet 21: 2759-2767.
Sébastien, M., P. Aubin, J. Brocard, J. Brocard, I. Marty, and J. Fauré. (2020). Dynamics of triadin, a muscle-specific triad protein, within sarcoplasmic reticulum subdomains. Mol. Biol. Cell 31: 261-272.
Shcheglovitov, A., O. Shcheglovitova, M. Yazawa, T. Portmann, R. Shu, V. Sebastiano, A. Krawisz, W. Froehlich, J.A. Bernstein, J.F. Hallmayer, and R.E. Dolmetsch. (2013). SHANK3 and IGF1 restore synaptic deficits in neurons from 22q13 deletion syndrome patients. Nature 503: 267-271.
Srikanth, S., M. Jew, K.D. Kim, M.K. Yee, J. Abramson, and Y. Gwack. (2012). Junctate is a Ca²⁺-sensing structural component of Orai1 and stromal interaction molecule 1 (STIM1). Proc. Natl. Acad. Sci. USA 109: 8682-8687.
Zhang, Z., J. Shrestha, C. Tateda, and J.T. Greenberg. (2014). Salicylic acid signaling controls the maturation and localization of the arabidopsis defense protein ACCELERATED CELL DEATH6. Mol Plant 7: 1365-1383.
Examples:
TC#	Name	Organismal Type	Example
8.A.28.1.1	Ankyrin-B of 3924 aas and 1 N-terminal TMS. Ankyrin-B plays roles in maintaining tissue cytoarchitecture, cell shape and biomechanical properties by promoting key protein:protein interactions required for membrane anchoring and organization of the spectrin-actin skeleton, scaffolding proteins and cell adhesive proteins (Rao and Maddala 2016).	Animals	*Ankyrin-B of Homo sapiens* (Q01484)**

8.A.28.1.2	Ankyrin-1 of 1881 aas. Small ankyrin 1 (sAnk1) is a 17-kDa transmembrane (TM) protein that binds to the cytoskeletal protein, obscurin, and stabilizes the network sarcoplasmic reticulum in skeletal muscle. It shares homology in its TM amino acid sequence with sarcolipin (TC# 1.A.50.2.1), a small protein inhibitor of the sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA; TC# 3.A.3.2.7). sAnk1 and SERCA1 interact in their transmembrane domains to regulate SERCA (Desmond et al. 2015; Desmond et al. 2017).		Ankryn 1 of Homo sapiens

8.A.28.1.3	Triadin of 729 aas. Contributes to the regulation of lumenal Ca²⁺ release via the sarcoplasmic reticulum calcium release channels RYR1 and RYR2, a key step in triggering skeletal and heart muscle contraction (Marty 2015). It is required for normal organization of the triad junction, where T-tubules and the sarcoplasmic reticulum terminal cisternae are in close contact. Triadin is required for normal skeletal muscle strength. It plays a role in excitation-contraction coupling in the heart and in regulating the rate of heart beats (Roux-Buisson et al. 2012). Triadin and junctin bind to different sites on RyR1; triadin plays an important role in ensuring rapid Ca²⁺ release during excitation-contraction coupling in skeletal muscle (Goonasekera et al. 2007). Althogh diffusible, a longer residence time in the ER-PM contact point is due to the transmembrane domain of T95 resulting in triad localization (Sébastien et al. 2020).		Triadin of Homo sapiens

8.A.28.1.4	Junctin 2 of 245 aas and 1 TMS, a core component if the RyR1 complex (see TC#1.A.3.1.2). Junctin, triadin and calsequestrin, are associated with the sarcopasmic reticulum in muscle cells. These SR proteins are not essential for survival but exert structural and functional influences that modify the gain of EC-coupling and maintain normal muscle function (Dulhunty et al. 2016).		Junctin of Mus musculus

8.A.28.1.5	Junctate, Junctin, Aspartate beta-hydroxylase, ASPH, BAH of 758 aas and 1 N-terminal TMS. It has enzyme activity, but is also a Ca²⁺-sensing ER protein, a structural component of ER-PM junctions where Orai1 and STIM1 cluster and interact in T cells (Srikanth et al. 2012). It plays a role in cardiac Ca²⁺ handeling (homeostatis), contractility and heart failure (Gergs et al. 2007). Two other proteins of the complex are: Triadin and Calsequestrin. Junctin is a transmembrane protein of striated muscles, located at the junctional sarcoplasmic reticulum (SR). It is characterized by a luminal C-terminal tail, through which it functionally interacts with calsequestrin and the ryanodine receptor (RyR). In non-muscle cells, junctin and calsequestrin assemble in long linear regions within the endoplasmic reticulum, mirroring the formation of calsequestrin polymers (Rossi et al. 2022). In differentiating myotubes, the two proteins colocalize at triads, where they assemble with other proteins of the junctional SR. Two KEKE motifs can bind calsequestrin, and stretches of charged amino acids downstream of these motifs can also bind calsequestrin and the RyR. Deletion of even one of these regions impaired the ability of junctin to localize at the junctional SR, suggesting that interaction with other proteins at this site represents a key element in junctin targeting (Rossi et al. 2022).		Junctin of Homo sapiens

8.A.28.1.6	A-kinase anchor protein 5, AKAP5; AKAP79, of 427 aas. Associates with to the beta2-adrenergic receptor (beta2-AR) to regulate the beta2-AR signaling pathway. Also binds directly to TrpV4 (TC# 1.A.4.2.5) (Mack and Fischer 2017).		AKAP5 of Homo sapiens

8.A.28.1.7	SH3 and multiple ankyrin repeat domains protein 3, SHANK3, or Proline-rich synapse-associated protein 2, PSAP2 or PROSAP2, of 1731 aas. It is a major scaffold postsynaptic density protein which interacts with multiple proteins and complexes. Interconnects receptors of the postsynaptic membrane including NMDA-type and metabotropic glutamate receptors via complexes with GKAP/PSD-95 and HOMER, respectively (Shcheglovitov et al. 2013). SHANK is regulated epigenetically and interacts with GluR1. It is a monogentic cause of autism (ASD) and schizophrenia (Monteiro and Feng 2017).		SHANK3 of Homo sapiens

8.A.28.1.8	Kinase D-interacting substrate of 220 kDa, KIDINS220 or ARMS, of 1771 aas and 4 central TMSs in a 2 + 2 TMS arrangement. It promotes a prolonged MAP-kinase signaling by neurotrophins through activation of a Rap1-dependent mechanism and provides a docking site for the CRKL-C3G complex, resulting in Rap1-dependent sustained ERK activation. It may also play an important role in regulating postsynaptic signal transduction through the syntrophin-mediated localization of receptor tyrosine kinases such as EPHA4 (Liao et al. 2007). Prenatal delineation of a distinct lethal fetal syndrome is caused by a homozygous truncating KIDINS220 variant (El-Dessouky et al. 2020). The ankyrin repeat domain is N-terminal. Kidins220 as an actor in an increasing number of pathologies characterized by astrocytic dysfunctions (Jaudon et al. 2021). It regulates the expression of the inwardly rectifying potassium channel, Kir 4.1 (TC# 1.A.2.1.16) (Jaudon et al. 2021).		ARMS of Homo sapiens

8.A.28.1.9	AnkyrinG (Andyrin3, Ank3) of 4377 aas and 0 TMSs. Neurons are highly polarized cells that face the fundamental challenge of compartmentalizing a vast and diverse repertoire of proteins in order to function properly (Eichel et al. 2022). The axon initial segment (AIS) is a specialized domain that separates a neuron's morphologically, biochemically and functionally distinct axon and dendrite compartments. in C. elegans, mouse, rat and human neurons, dendritically and axonally polarized transmembrane proteins are recognized by endocytic machinery in the AIS, robustly endocytosed and targeted to late endosomes for degradation. Forcing receptor interaction with the AIS master organizer, ankyrinG, antagonizes receptor endocytosis in the AIS, causes receptor accumulation in the AIS, and leads to polarity deficits with subsequent morphological and behavioural defects. Therefore, endocytic removal of polarized receptors that diffuse into the AIS serves as a membrane-clearance mechanism that is likely to work in conjunction with the known AIS diffusion-barrier mechanism to maintain neuronal polarity on the plasma membrane. This reveals a conserved endocytic clearance mechanism in the AIS to maintain neuronal polarity by reinforcing axonal and dendritic compartment membrane boundaries (Eichel et al. 2022).		AnkyrinG of Homo sapiens