The voltage-gated proton channel Hv1/VSOP inhibits neutrophil granule release

Abstract

Neutrophil granule exocytosis is crucial for host defense and inflammation. Neutrophils contain 4 types of granules, the exocytotic release of which is differentially regulated. This exocytosis is known to be driven by diverse mediators, including calcium and nucleotides, but the precise molecular mechanism remains largely unknown. We show in the present study that voltage-gated proton (Hv) channels are necessary for the proper release of azurophilic granules in neutrophils. On activation of NADPH oxidase by PMA and IgG, neutrophils derived from Hvcn1 gene knockout mouse exhibited greater secretion of MPO and elastase than WT cells. In contrast, release of LTF enriched in specific granules was not enhanced in these cells. The excess release of azurophilic granules in Hv1/VSOP-deficient neutrophils was suppressed by inhibiting NADPH oxidase activity and, in part, by valinomycin, a potassium ionophore. In addition, Hv1/VSOP-deficient mice exhibited more severe lung inflammation after intranasal Candida albicans infection than WT mice. These findings suggest that the Hv channel acts to specifically dampen the release of azurophilic granules through, in part, the suppression of increased positive charges at the plasma membrane accompanied by the activation of NADPH oxidase in neutrophils.

Unconventional role of voltage‐gated proton channels (VSOP/Hv1) in regulation of microglial ROS production

“…We also performed the experiments using Hvcn1 gene‐trap ( Hvcn1 ‐GT) mice which have widely been used as Hvcn1 ‐deficient animals (Okochi et al . , ; Ramsey et al . ; El Chemaly et al .…”

“…For the primary antibody, rabbit polyclonal anti‐Hv1/VSOP antibody (Okochi et al . , ) diluted 1 : 500 (Fig. ) or goat polyclonal anti‐p67 antibody (N‐19; Santa Cruz, Santa Cruz, CA, USA) diluted 1 : 200 (Fig.…”

Comparison between mouse and sea urchin orthologs of voltage-gated proton channel suggests role of S3 segment in activation gating

“…Hv1 plays a crucial role in production of reactive oxygen species [8][9][10][11][12][13][14][15][16][17][18]. A gene encoding a voltage-gated proton channel, HVCN1, has been identified from human, mouse, ascidian [19,20], insect [21], dinoflagellates [22], marine phytoplankton [23] and in other metazoans.…”

Calcium signalling and related ion channels in neutrophil recruitment and function

“…The proton channel murine voltage‐sensing domain only protein (VSOP) and its human homologue Hv1 have been shown to inhibit azurophilic granule release in neutrophils. VSOP/Hv1 −/− deficient neutrophils displayed an enhanced release of MPO and neutrophil elastase compared to WT cells when activated with PMA . Furthermore, VSOP/Hv1 was described to play an important role in NADPH oxidase‐mediated phagosomal ROS production in neutrophils by counterbalancing the oxidase induced cytosolic acidification and cell depolarization .…”