Annexin A2 Regulates TRPA1-Dependent Nociception

Abstract

The transient receptor potential A1 (TRPA1) channel is essential for vertebrate pain. Even though TRPA1 activation by ligands has been studied extensively, the molecular machinery regulating TRPA1 is only poorly understood. Using an unbiased proteomics-based approach we uncovered the physical association of Annexin A2 (AnxA2) with native TRPA1 in mouse sensory neurons. AnxA2 is enriched in a subpopulation of sensory neurons and coexpressed with TRPA1. Furthermore, we observe an increase of TRPA1 membrane levels in cultured sensory neurons from AnxA2-deficient mice. This is reflected by our calcium imaging experiments revealing higher responsiveness upon TRPA1 activation in AnxA2-deficient neurons. In vivo these findings are associated with enhanced nocifensive behaviors specifically in TRPA1-dependent paradigms of acute and inflammatory pain, while heat and mechanical sensitivity as well as TRPV1-mediated pain are preserved in AnxA2-deficient mice. Our results support a model whereby AnxA2 limits the availability of TRPA1 channels to regulate nociceptive signaling in vertebrates.

Annexins – insights from knockout mice

“…Increased levels of TRPA1 at the plasma membrane of AnxA2-deficient sensory neurons and enhanced TRPA1-dependent pain in AnxA2 -/-mice were observed. This may indeed be the first in vivo evidence to support several examples that linked AnxA2/p11 with ion channels (Gerke and Moss, 2002;Gerke et al, 2005;Avenali et al, 2014). Finally, inoculation of prostate cancer cells mixed with bone marrow stromal cells from the AnxA2 KO mice revealed that AnxA2 binding to stromal-derived factor 1 is crucial for recruitment, growth and survival of prostate cancer cells in the bone marrow microenvironment (Jung et al, 2015).…”

“…In addition, in sensory neurons, AnxA2 is a ligand for the transient receptor potential ion channel A1 (TRPA1) (Avenali et al, 2014), which is essential for detection of harmful chemicals, tissue damage and chronic pain. Increased levels of TRPA1 at the plasma membrane of AnxA2-deficient sensory neurons and enhanced TRPA1-dependent pain in AnxA2 -/-mice were observed.…”

Nocistatin sensitizes TRPA1 channels in peripheral sensory neurons

“…9 Untransfected neurons were grown for 16-24 h before being used for experiments. Transfection of neurons was achieved by nucleofection of siRNA into freshly isolated DRG neurons using the P3 Primary Cell 4D Nucleofector X Kit with the 4D-Nucleofector X Unit according to the manufacturer's instructions (Lonza AG).…”

“…Ratiometric calcium imaging was performed essentially as described previously 9 using an inverted microscope (Zeiss Axio Observer Z1). Briefly, cells were washed 3 times with calcium imaging buffer consisting of 1£HBSS (1.3 mM calcium) supplemented with 10 mM HEPES.…”

“…We recently characterized AnxA2 as a TRPA1-associated protein that limits TRPA1 membrane abundance and appears to regulate its activity both in vitro and in vivo. 9 Tmem100 is yet another modulator of protein complexes harboring TRPA1 and TRPV1 (commonly known as the vanilloid receptor). Tmem100 has been shown to associate with TRPA1 and TRPV1 in sensory neurons where it potentiates TRPA1 activity in a TRPV1-dependent manner.…”