Molecular basis for PP2A regulatory subunit B56α targeting in cardiomyocytes

Bhasin, Naina; Cunha, Shane R.; Mudannayake, Malkanthi; Gigena, Marisa S.; Rogers, Terry B.; Mohler, Peter J.

doi:10.1152/ajpheart.00059.2007

Cited by 89 publications

(104 citation statements)

References 89 publications

Supporting

Mentioning

103

Contrasting

Order By: Relevance

“…9). This domain is also a binding partner for protein phosphatase 2A regulatory subunit B56␣ (10). Finally, ankyrin-B contains a C-terminal regulatory domain (RD) comprised of a death domain and an ϳ300-amino acid extended random coil (11).…”

mentioning

confidence: 99%

Obscurin Targets Ankyrin-B and Protein Phosphatase 2A to the Cardiac M-line

Cunha

Mohler

2008

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Ankyrin-B targets ion channels and transporters in excitable cells. Dysfunction in ankyrin-B-based pathways results in defects in cardiac physiology. Despite a wealth of knowledge regarding the role of ankyrin-B for cardiac function, little is known regarding the mechanisms underlying ankyrin-B regulation. Moreover, the pathways underlying ankyrin-B targeting in heart are unclear. We report that alternative splicing regulates ankyrin-B localization and function in cardiomyocytes. Specifically, we identify a novel exon (exon 43) in the ankyrin-B regulatory domain that mediates interaction with the Rho-GEF obscurin. Ankyrin-B transcripts harboring exon 43 represent the primary cardiac isoform in human and mouse. We demonstrate that ankyrin-B and obscurin are co-localized at the M-line of myocytes and co-immunoprecipitate from heart. We define the structural requirements for ankyrin-B/obscurin interaction to two motifs in the ankyrin-B regulatory domain and demonstrate that both are critical for obscurin/ankyrin-B interaction.In addition, we demonstrate that interaction with obscurin is required for ankyrin-B M-line targeting. Specifically, both obscurin-binding motifs are required for the M-line targeting of a GFP-ankyrin-B regulatory domain. Moreover, this construct acts as a dominant-negative by competing with endogenous ankyrin-B for obscurin-binding at the M-line, thus providing a powerful new tool to evaluate the function of obscurin/ ankyrin-B interactions. With this new tool, we demonstrate that the obscurin/ankyrin-B interaction is critical for recruitment of PP2A to the cardiac M-line. Together, these data provide the first evidence for the molecular basis of ankyrin-B and PP2A targeting and function at the cardiac M-line. Finally, we report that ankyrin-B R1788W is localized adjacent to the ankyrin-B obscurin-binding motif and increases binding activity for obscurin. In summary, our new findings demonstrate that ANK2 is subject to alternative splicing that gives rise to unique polypeptides with diverse roles in cardiac function.Ankyrins are adapter proteins that facilitate the local organization of integral membrane proteins with cytoskeletal elements. Three human ankyrin genes ANK1, ANK2, and ANK3 encode polypeptides termed ankyrin-R, ankyrin-B, and ankyrin-G, respectively. Ankyrins-B and -G are ubiquitously expressed, whereas ankyrin-R has restricted distribution. Ankyrin-B is required for normal cardiac physiology, and ankyrin-B dysfunction in humans and mice results in disease. Specifically, mice lacking ankyrin-B die at postnatal day 1 (1). Mice heterozygous for a null mutation in ankyrin-B (ankyrin-B ϩ/Ϫ mice) display bradycardia, heart rate variability, conduction defects, prolonged rate corrected QT intervals, catecholaminergic polymorphic ventricular tachycardia, syncope, and sudden cardiac death (2). ANK2 (encodes ankyrin-B) lossof-function variants in humans result in dominantly inherited human arrhythmia termed "ankyrin-B syndrome" or "type 4 long QT syndrome." Human disease phenotypes includ...

show abstract

mentioning

confidence: 99%

Obscurin Targets Ankyrin-B and Protein Phosphatase 2A to the Cardiac M-line

Cunha

Mohler

2008

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…PP2A/BЈ␤ also preferentially binds to the kinase Pim-1 to promote its degradation (36). Ankyrin-B, a linker between the actin cytoskeleton and membrane receptors and ion channels, binds to the variable C-terminal tail of the BЈ␣ regulatory subunit (6). The same PP2A regulatory subunit also selectively interacts with and downregulates c-myc (3), while PP2A/BЈ␥ interacts with and dephosphorylates the tumor suppressor p53 (32) and PP2A/BЈ␦ preferentially binds to the dual-specificity phosphatase and mitotic activator Cdc25 (38).…”

Section: Discussionmentioning

confidence: 99%

“…Endogenous B subunits associate with TrkA and regulate its activity. The mammalian BЈ subunit gene family gives rise to five gene products (␣, ␤, ␥, ␦, and ε) with a highly conserved tandem ␣-helical repeat region that interacts with both A and C subunits (12,67), while the divergent N and C termini may be involved in binding to specific substrates and anchoring proteins (6). To determine if BЈ subunits can recruit PP2A to the NGF receptor, we immunoprecipitated endogenous TrkA from PC12 cells that inducibly express BЈ␤.…”

Section: Pp2a Sustains Ngf-dependent Trka Autophosphorylationmentioning

confidence: 99%

The Protein Phosphatase 2A Regulatory Subunits B′β and B′δ Mediate Sustained TrkA Neurotrophin Receptor Autophosphorylation and Neuronal Differentiation

Kanegan

Strack

2009

Molecular and Cellular Biology

View full text Add to dashboard Cite

Nerve growth factor (NGF) is critical for the differentiation and maintenance of neurons in the peripheral and central nervous system. Sustained autophosphorylation of the TrkA receptor tyrosine kinase and longlasting activation of downstream kinase cascades are hallmarks of NGF signaling, yet our knowledge of the molecular mechanisms underlying prolonged TrkA activity is incomplete. Protein phosphatase 2A (PP2A) is a heterotrimeric Ser/Thr phosphatase composed of a scaffolding, catalytic, and regulatory subunit (B, B, and B؆ gene families). Here, we employ a combination of pharmacological inhibitors, regulatory subunit overexpression, PP2A scaffold subunit exchange, and RNA interference to show that PP2A containing B family regulatory subunits participates in sustained NGF signaling in PC12 cells. Specifically, two neuron-enriched regulatory subunits, B␤ and B␦, recruit PP2A into a complex with TrkA to dephosphorylate the NGF receptor on Ser/Thr residues and to potentiate its intrinsic Tyr kinase activity. Acting at the receptor level, PP2A/ B␤ and B␦ enhance NGF (but not epidermal growth factor or fibroblast growth factor) signaling through the Akt and Ras-mitogen-activated protein kinase cascades and promote neuritogenesis and differentiation of PC12 cells. Thus, select PP2A heterotrimers oppose desensitization of the TrkA receptor tyrosine kinase, perhaps through dephosphorylation of inhibitory Ser/Thr phosphorylation sites on the receptor itself, to maintain neurotrophinmediated developmental and survival signaling.

show abstract

“…However, we now know that human disease, particularly excitable cell disease, may be caused by defects in non-ion channel polypeptides including in cellular components residing well beneath the plasma membrane. For example, over the past few years, a new class of potentially fatal cardiac arrhythmias has been linked with cytoplasmic proteins that include sub-membrane adapters such as ankyrin-B (ANK2) [1][2][3][4][5] , ankyrin-G (ANK3) [6][7][8] , and alpha-1 syntrophin [9] , membrane coat proteins including caveolin-3 (CAV3) [10] , signaling platforms including yotiao (AKAP9) [11,12] , and cardiac enzymes (GPD1L) [13] . The focus of this review is to detail the exciting role of lamins, yet another class of gene products that have provided elegant new insight into human disease.…”

Section: Introductionmentioning

confidence: 99%