Regulation of L-type Voltage Gated Calcium Channel CACNA1S in Macrophages upon Mycobacterium tuberculosis Infection.

Cecil Antony,Yogendra Singh,Brijendra K Tiwari,Krishnamurthy Natarajan,Subhash Mehto,Selvakumar Subbian

doi:10.1371/journal.pone.0124263

Cecil Antony, Yogendra Singh + Show 4 more

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https://doi.org/10.1371/journal.pone.0124263

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Abstract

We demonstrated earlier the inhibitory role played by Voltage Gated Calcium Channels (VGCCs) in regulating Mycobacterium tuberculosis (M. tb) survival and pathogenesis. In this report, we investigated mechanisms and key players that regulate the surface expression of VGCC-CACNA1S by Rv2463 and M. tb infection in macrophages. Our earlier work identified Rv2463 to be expressed at early times post infection in macrophages that induced suppressor responses to dendritic cells and macrophages. Our results in this study demonstrate a role of MyD88 independent TLR pathway in mediating CACNA1S expression. Dissecting the role for second messengers, we show that calcium homeostasis plays a key role in CACNA1S expression during M. tb infection. Using siRNAs against molecular sensors of calcium regulation, we show an involvement of ER associated Stromal Interaction Molecules 1 and 2 (STIM1 and STIM2), and transcription factor pCREB, towards CACNA1S expression that also involved the MyD88 independent pathway. Interestingly, reactive oxygen species played a negative role in M. tb mediated CACNA1S expression. Further, a cross-regulation of ROS and pCREB was noted that governed CACNA1S expression. Characterizing the mechanisms governing CACNA1S expression would improve our understanding of the regulation of VGCC expression and its role in M. tb pathogenesis during M. tb infection.

Highlights

Tuberculosis, caused by its etiological agent Mycobacterium tuberculosis (M. tb), remains a major killer till date [1]. 2012 estimates of WHO put the figures of people infected with M. tb at 8.3 million new cases with 1.3 million deaths annually [2]
Since we demonstrated the inhibitory role of Voltage Gated Calcium Channels (VGCCs) [37], we hypothesized that Rv2463 could regulate the expression of CACNA1S, a calcium channel whose expression and regulation has been detected in T cell subsets but not in macrophages, especially in the context of M. tb infection
To begin with we investigated the ability of Rv2463 to modulate CACNA1S expression in mouse macrophages

Summary

Introduction

Tuberculosis, caused by its etiological agent Mycobacterium tuberculosis (M. tb), remains a major killer till date [1]. 2012 estimates of WHO put the figures of people infected with M. tb at 8.3 million new cases with 1.3 million deaths annually [2]. M. tb prevents phagolysosome fusion [6] and remains undetected within phagosomes, inhibits. A key molecule that regulates many of these processes during infections is calcium [10, 11]. Calcium plays a definite role in regulating the pathogenesis of M. tb [10,11,12] that include activation of transcription factors, mediating phagolysosome fusion, cell survival etc [13,14,15]. A key process that is regulated by CREB in macrophages is the activation of anti-apoptotic pathway. A number of pathogens such as Shigella, Salmonella and Yersinia utilize this mechanism to activate CREB via calcium influx and suppress protective immune responses [17,18]. CREB induced TNF-alpha production promoted anti-apoptotic responses in macrophages [20]

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