Astrocytes express functional TRPV2 ion channels

doi:10.1016/j.bbrc.2013.10.046

Biochemical and Biophysical Research Communications

Volume 441, Issue 2, 15 November 2013, Pages 327-332

https://doi.org/10.1016/j.bbrc.2013.10.046 Get rights and content

Highlights

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TRPV2 protein is expressed in astrocytes.
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Astrocytes can respond to noxious heat stimulus through TRPV2 activation.
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An endogenous lipid, lysophosphatidylcholine activates TRPV2 in astrocytes.

Abstract

Thermosensitive transient receptor potential (thermo TRP) channels are important for sensory transduction. Among them, TRPV2 has an interesting characteristic of being activated by very high temperature (>52 °C). In addition to the heat sensor function, TRPV2 also acts as a mechanosensor, an osomosensor and a lipid sensor. It has been reported that TRPV2 is expressed in heart, intestine, pancreas and sensory nerves. In the central nervous system, neuronal TRPV2 expression was reported, however, glial expression and the precise roles of TRPV2 have not been determined. To explore the functional expression of TRPV2 in astrocytes, the expression was determined by histological and physiological methods. Interestingly, TRPV2 expression was detected in plasma membrane of astrocytes, and the astrocytic TRPV2 was activated by very high temperature (>50 °C) consistent with the reported characteristic. We revealed that the astrocytic TRPV2 was also activated by lysophosphatidylcholine, a known endogenous lipid ligand for TRPV2, suggesting that astrocytic TRPV2 might regulate neuronal activities in response to lipid metabolism. Thus, for the first time we revealed that TRPV2 is functionally expressed in astrocytes in addition to neurons.

Introduction

TRPV2 was originally cloned as a heat sensor and is well known to be activated by very high temperature (>52 °C) [1]. TRPV2 was also reported to be a mechano-sensor [2], [3], [4], [5]. Recently, we reported that the mechanosenitive characteristics of TRPV2 regulated axonal outgrowth in developing neurons [4], and also regulated peristalsis of intestine [5]. It was also reported that insulin like growth factor I (IGF-I) promoted TRPV2 surface expression and activity [6]. Chemical ligands such as 2-aminoethoxydiphenyl borate (2-APB) and probenecid also activate TRPV2 [7], [8]. Lysophosphatidylcholine (LPC) acts as an endogenous ligand for activation of TRPV2 [9]. In central nervous system, TRPV2 expression was reported in striatal, hippocampal and hypothalamic neurons [10], [11], [12], [13], [14].

In addition to neurons, glial cells are important to maintain our brain function. Notably, astrocytes provide metabolic support and eliminate waste products, such as neurotransmitters, from extracellular spaces [15]. They also regulate blood flow depending on neuronal activity [16], [17]. Furthermore, astrocytes are essential for bidirectional communication with neurons, and thus can modulate neuronal activity [18], [19]. Although TRPV2 expression was confirmed in neurons, the expressions in astrocytes remain poorly understood. In this study, we examined whether functional TRPV2 expressed in astrocytes by using a combination of histological and physiological methods.

Section snippets

Animals

C57BL/6J mice were used for the study. All animal care and procedures were performed according to Gunma University guidelines.

Immunohistochemical analysis

Immunohistochemistry were performed as previously described [20], [21]. The following antibodies were used; rabbit polyclonal anti-TRPV2 antibody (1:200, Transgenic [4]), mouse anti-GFAP (1:500, Sigma) antibody.

Reverse transcription PCR

The TRPV channels expressions were examined by reverse transcription PCR (RT-PCR). Total RNA was prepared from the DRG of adult ICR mice using TRIzol reagent

Results and discussion

We first determined whether TRPV2 expression was observed in brain sections by immunohistochemical analysis utilizing reported specific anti-TRPV2 antibody [4]. Specificity of the antibody was confirmed as described by our previous work [4]. In cerebellum, strong TRPV2 expressions were observed in molecular layer (ML) and Purkinje cell layer (PL) consistent with previous reports (Fig. 1A), which neurons expressed TRPV2 [10], [11], [12], [13], [14]. In addition to the cerebellar neurons, GFAP, a

Acknowledgments

We thank Drs. K. Ikenaka, M. Tominaga (NIPS, Okazaki) and my lab members for helpful discussion. This research was supported by Grants-in-Aid for Scientific Research (Project No. 21200012, 20399554, 24111507 “Brain Environment” to K.S., 23650159 to Y.I.) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, by a Grant from Uehara Memorial Foundation (to K.S.), by a Grant from Takeda Science Foundation, Tokyo, Japan (to K.S. and Y.I.), by a Grant from the Sumitomo

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View full text

Astrocytes express functional TRPV2 ion channels

Highlights

Abstract

Introduction

Section snippets

Animals

Immunohistochemical analysis

Reverse transcription PCR

Results and discussion

Acknowledgments

Neurosci. Lett.

J. Biol. Chem.

Biochim. Biophys. Acta

Brain Res.

Exp. Neurol.

Brain Res.

Gene Expr. Patterns

Biochem. Biophys. Res. Commun.

A capsaicin-receptor homologue with a high threshold for noxious heat

Nature

The mechanosensitive nature of TRPV channels

Pflugers Arch.

TRPV2 is a component of osmotically sensitive cation channels in murine aortic myocytes

Circ. Res.