Requirement for AHNAK1-mediated calcium signaling during T lymphocyte cytolysis

Matza, Didi; Badou, Abdallah; Jha, Mithilesh Kumar; Willinger, Tim; Antov, Andrey; Sanjabi, Shomyseh; Kobayashi, Koichi S.; Marchesi, V.; Flavell, Richard A.

doi:10.1073/pnas.0902844106

Cited by 46 publications

(50 citation statements)

References 38 publications

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“…Interestingly, AHNAK1 is expressed in CD8 + T cells only after they differentiate to CTLs, and expression of Cav1.1 is upregulated in parallel. Like AHNAK1 −/− CD4 + T cells, CTLs from AHNAK1 −/− mice show reduced Ca 2+ elevation in response to TCR stimulation, as well as reduced granzyme B production and cytolytic activity (186). …”

Section: Other Pathways For Ca2+ Entry In Lymphocytesmentioning

confidence: 99%

Molecular Basis of Calcium Signaling in Lymphocytes: STIM and ORAI

Hogan

Lewis

Rao

2010

Annu. Rev. Immunol.

677

717

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Ca 2+ entry into cells of the peripheral immune system occurs through highly Ca 2+ -selective channels known as CRAC (calcium release-activated calcium) channels. CRAC channels are a very wellcharacterized example of store-operated Ca 2+ channels, so designated because they open when the endoplasmic reticulum (ER) Ca 2+ store becomes depleted. Physiologically, Ca 2+ is released from the ER lumen into the cytoplasm when activated receptors couple to phospholipase C and trigger production of the second messenger inositol 1,4,5-trisphosphate (IP 3 ). IP 3 binds to IP 3 receptors in the ER membrane and activates Ca 2+ release. The proteins STIM and ORAI were discovered through limited and genome-wide RNAi screens, respectively, performed in Drosophila cells and focused on identifying modulators of store-operated Ca 2+ entry. STIM1 and STIM2 sense the depletion of ER Ca 2+ stores, whereas ORAI1 is a pore subunit of the CRAC channel. In this review, we discuss selected aspects of Ca 2+ signaling in cells of the immune system, focusing on the roles of STIM and ORAI proteins in store-operated Ca 2+ entry. KeywordsCRAC channels; store-operated calcium entry; T cell activation; primary immunodeficiencies OVERVIEW Ca 2+ signaling is essential for diverse biological processes (reviewed in 1 -4). Ca 2+ ions are especially suited as intracellular second messengers because of the strong homeostatic mechanisms that maintain intracellular free Ca 2+ concentrations ([Ca 2+ ] i ) in resting cells at 100 nM or less, in the face of extracellular Ca 2+ concentrations ([Ca 2+ ] o ) that are four orders of magnitude higher (1-2 mM). Cytoplasmic Ca 2+ concentrations are maintained at low levels primarily through the action of plasma membrane Ca 2+ -ATPases (PMCAs) that pump Ca 2+ out of the cell across the plasma membrane, and the sarco-endoplasmic reticulum Ca 2+ -ATPases (SERCAs) that pump Ca 2+ into the lumen of the endoplasmic reticulum (ER) ( Figure 1). Secondary regulators of [Ca 2+ ] i include the mitochondrial Ca 2+ uniporter (MCU) that transports Ca 2+ across the inner mitochondrial membrane and the electrogenic Na + -Ca 2+

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Section: Other Pathways For Ca2+ Entry In Lymphocytesmentioning

confidence: 99%

Molecular Basis of Calcium Signaling in Lymphocytes: STIM and ORAI

Hogan

Lewis

Rao

2010

Annu. Rev. Immunol.

677

717

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“…[Ca 2+ ] i increase upon T-cell receptor activation was determined in activated T-cell blasts as described earlier [60,61,62]. T lymphocytes were incubated with anti-CD3 (1 μl/ml; 145-2C11, R&D Systems) for 30 min on ice and subsequently loaded with Fura-2AM (2 µM, Molecular Probes, Goettingen, Germany) for 15 min at 37°C.…”

Section: Methodsmentioning

confidence: 99%

“…24h after cells were placed in the 96-well plate, 20 µl of the MTS/PMS solution was added directly to each well and incubated for 4h. The absorbance was measured at 490 nm with a reference wavelength at 690 nm using an ELISA plate reader (PowerWave XS2, BioTek, VT, USA) [60,61,62]. …”

Section: Methodsmentioning

confidence: 99%

AMPKα1-Sensitivity of Orai1 and Ca<sup>2+</sup> Entry in T - Lymphocytes

Bhavsar

Schmidt²,

Bobbala³

et al. 2013

Cell Physiol Biochem

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Background/Aims: T-lymphocyte activation and function critically depends on Ca²⁺ signaling, which is regulated by store operated Ca²⁺ entry (SOCE). Human and mouse T lymphocytes express AMP activated kinase AMPKα1, which is rapidly activated following elevation of cytosolic Ca²⁺ concentration ([Ca²⁺]_i) by treatment of the cells with Ca²⁺ ionophore or following inhibition of endosomal Ca²⁺ ATPase with thapsigargin. AMPK is further activated by triggering of the T cell antigen receptor (TCR). The present study explored whether AMPK influences Ca²⁺ entry and Ca²⁺-sensitive regulation of T-lymphocyte function. Methods: T-lymphocytes were isolated and cultured from AMPKα1-deficient (ampk^-/-) mice and from their wildtype (ampk^+/+) littermates. The phenotype of the cells was analysed by flow cytometry, [Ca²⁺]_i estimated from Fura-2 fluorescence, SOCE from increase of [Ca²⁺]_i following thapsigargin treatment (1 µM), and cell function analysed by measuring cytokine secretion and western blotting. Results: Expression of surface markers in CD4⁺ and CD8⁺ T-cells were similar in ampk^-/- and ampk^+/+ T-lymphocyte blasts. Moreover, total STIM1 protein abundance was similar in ampk^-/- and ampk^+/+ T-lymphocyte blasts. However, Orai1 cell membrane protein abundance was significantly higher in ampk^-/- than in ampk^+/+ T-lymphocyte blasts. SOCE and increase of [Ca²⁺]_i following TCR activation by triggering TCR with anti-CD3 and cross-linking secondary antibody were both significantly more pronounced in ampk^-/- than in ampk^+/+ T-lymphocyte blasts. The difference of Ca²⁺ entry between ampk^-/- and ampk^+/+ T-lymphocytes was abrogated by Orai1 inhibitor 2-aminoethoxydiphenyl borate (2-APB, 50 µM). Proliferation of unstimulated ampk^-/- lymphocytes was higher than proliferation of ampk^+/+ T-lymphocytes, a difference reversed by Orai1 silencing. Conclusions: AMPK downregulates Orai1 and thus SOCE in T-lymphocytes and thus participates in negative feed-back regulation of cytosolic Ca²⁺ activity.

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“…Sub-cellular localization of AHNAK depends on the cell type and on extracellular calcium concentration [10]. AHNAK is also known to be a key player in calcium signaling and calcium channel function [11][12][13][14][15][16][17][18]. In the presence of arachidonic acid, AHNAK is known to bind and activate phospholipase C gamma to generate 2 second messengers that regulate the calcium flux [19,20].…”

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confidence: 99%

AHNAK KO Mice are Protected from Diet-Induced Obesity but are Glucose Intolerant

et al. 2014

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AHNAK is a 700 KD phosphoprotein primarily involved in calcium signaling in various cell types and regulating cytoskeletal organization and cell membrane architecture. AHNAK expression has also been associated with obesity. To investigate the role of AHNAK in regulating metabolic homeostasis, we studied whole body AHNAK knockout mice (KO) on either regular chow or high-fat diet (HFD). KO mice had a leaner phenotype and were resistant to high-fat diet-induced obesity (DIO), as reflected by a reduction in adipose tissue mass in conjunction with higher lean mass compared to wild-type controls (WT). However, KO mice exhibited higher fasting glucose levels, impaired glucose tolerance, and diminished serum insulin levels on either diet. Concomitantly, KO mice on HFD displayed defects in insulin signaling, as evident from reduced Akt phosphorylation and decreased cellular glucose transporter (Glut4) levels. Glucose intolerance and insulin resistance were also associated with changes in expression of genes regulating fat, glucose, and energy metabolism in adipose tissue and liver. Taken together, these data demonstrate that (a) AHNAK is involved in glucose homeostasis and weight balance (b) under normal feeding KO mice are insulin sensitive yet insulin deficient; and (c) AHNAK deletion protects against HFD-induced obesity, but not against HFD-induced insulin resistance and glucose intolerance in vivo.

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Requirement for AHNAK1-mediated calcium signaling during T lymphocyte cytolysis

Cited by 46 publications

References 38 publications

Molecular Basis of Calcium Signaling in Lymphocytes: STIM and ORAI

Molecular Basis of Calcium Signaling in Lymphocytes: STIM and ORAI

AMPKα1-Sensitivity of Orai1 and Ca<sup>2+</sup> Entry in T - Lymphocytes

AHNAK KO Mice are Protected from Diet-Induced Obesity but are Glucose Intolerant

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