Abstract
The vacuolar proton-pumping ATPase (V-ATPase) is the main mediator of intracellular organelle acidification and also regulates transmembrane proton (H+) secretion, which is necessary for an array of physiological functions fulfilled by organs such as the kidney, male reproductive tract, lung, bone, and ear. In this study we characterize expression of the V-ATPase in the main olfactory epithelium of the mouse, as well as a functional role for the V-ATPase in odor detection. We report that the V-ATPase localizes to the apical membrane microvilli of olfactory sustentacular cells and to the basolateral membrane of microvillar cells. Plasma membrane V-ATPases containing the B1 subunit isoform are not detected in olfactory sensory neurons or in the olfactory bulb. This precise localization of expression affords the opportunity to ascertain the functional relevance of V-ATPase expression upon innate, odor-evoked behaviors in B1-deficient mice. This animal model exhibits diminished innate avoidance behavior (revealed as a decrease in freezing time and an increase in the number of sniffs in the presence of trimethyl-thiazoline) and diminished innate appetitive behavior (a decrease in time spent investigating the urine of the opposite sex). We conclude that V-ATPase-mediated H+ secretion in the olfactory epithelium is required for optimal olfactory function.
Highlights
The vacuolar proton-translocating ATPase plays an essential role in numerous vesicle trafficking processes
When expressed at the plasma membrane, the V-ATPase performs various cell typespecific functions: in renal collecting duct A-type intercalated cells, it is the main mediator of acid secretion by the kidney, maintaining body acid-base homeostasis [1,2,3,4]; in epididymal clear cells, it is responsible for the acidification of the luminal fluid that is necessary for sperm storage and maturation [5,6,7]; in neutrophils and macrophages, it regulates cytosolic pH [8,9]; in interdental cells of the inner ear, it is involved in regulating the pH of the endolymph [10,11,12]; and in osteoclasts, it is required for bone resorption [13,14,15,16]
Given that the olfactory epithelium (OE) has been implicated in acid-base sensing and/or regulation [17] and that this tissue expresses carbonic anhydrase [17,18,19,20,21], an enzyme which is highly expressed in H+-secreting cells in other tissues, we investigated whether the V-ATPase is expressed in this tissue
Summary
The vacuolar proton-translocating ATPase (vacuolar, or Vtype, H+ATPase, or V-ATPase) plays an essential role in numerous vesicle trafficking processes. We investigate the involvement of this enzyme in olfactory function through behavioral studies in mice that are null for the critical B1 subunit of the VATPase.
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