Table 1.

Types of functions proposed for H_V1 in different cells. Functions proposed for H_V1 in various cells are sorted into the four main effects of H_V1 activity, in some cases arbitrarily. NOX is NADPH oxidase. BCR is B cell receptor. V_m is membrane potential.

cell	↑pHi	↓pHo	regulate Vm	charge compensation
dinoflagellates	trigger bioluminescent flash [1,3]; feeding [2]		proton action potential [3]
coccolithophores	calcification [10]
insect	acid extrusion [11]
snail neurons	acid extrusion [4,12,13]	acidification of confined spaces [14]		ROS production for host defence [15]
amphibian oocyte	maturation, fertilization [16,17]		Vm oscillations [18]
zebra fish				neutrophils [19]
respiratory epithelium	acid extrusion [20]	optimize pH of airway surface fluid [21]; CO2 extrusion [22]		facilitate DUOX1 activity [23]
skeletal myotubes	acid extrusion [24]
phagocyte	optimize pHi for NOX [25–27]	phagosome pH and volume [28,29]	regulate Vm [28,30]; avoid apoptosis [31]	prevent NOX self-inhibition at high potentials [32–34]
microglia	optimize pHi for NOX [35]; volume regulation [36]			ROS production [35,37]
basophil	histamine secretion [38]
cardiac myocytes		CO2 elimination [39]
cardiac fibroblasts			regulate Vm [40]
osteoclasts	acid extrusion [41]		regulate Vm [41]
sperm	alkaline pHi triggers capacitation [42]			ROS production by NOX5 mediates motility [43]
cancer cells	tumour growth [44]	metastasis [44]
B lymphocyte				ROS production in BCR signalling [7,45]
malignant B cells				short isoform promotes proliferation [8]
kidney	acid extrusion [46]			Na+-dependent ROS production [47]