Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA.
Mol Hum Reprod. 2013 Jan;19(1):17-28. doi: 10.1093/molehr/gas040. Epub 2012 Sep 15.
Mammalian spermatogenesis and sperm maturation are susceptible to the effects of internal and external factors. However, how male germ cells interact with and respond to these elements including those potentially toxic substances is poorly understood. Here, we show that many bitter-taste receptors (T2rs), which are believed to function as gatekeepers in the oral cavity to detect and innately prevent the ingestion of poisonous bitter-tasting compounds, are expressed in mouse seminiferous tubules. Our in situ hybridization results indicate that Tas2r transcripts are expressed postmeiotically. Functional analysis showed that mouse spermatids and spermatozoa responded to both naturally occurring and synthetic bitter-tasting compounds by increasing intracellular free calcium concentrations, and individual male germ cells exhibited different ligand-activation profiles, indicating that each cell may express a unique subset of T2r receptors. These calcium responses could be suppressed by a specific bitter-tastant blocker or abolished by the knockout of the gene for the G protein subunit α-gustducin. Taken together, our data strongly suggest that male germ cells, like taste bud cells in the oral cavity and solitary chemosensory cells in the airway, utilize T2r receptors to sense chemicals in the milieu that may affect sperm behavior and fertilization.
哺乳动物的精子发生和精子成熟容易受到内外因素的影响。然而，男性生殖细胞如何与这些因素相互作用并作出反应，包括那些潜在的有毒物质，目前还知之甚少。在这里，我们表明许多苦味受体（T2r）在小鼠生精小管中表达，这些受体被认为在口腔中作为守门员，用于检测和先天防止摄入有毒的苦味化合物。我们的原位杂交结果表明，Tas2r 转录本在后减数分裂期表达。功能分析表明，小鼠精原细胞和精子对天然和合成的苦味化合物作出反应，增加细胞内游离钙浓度，并且单个生精细胞表现出不同的配体激活谱，表明每个细胞可能表达独特的一组 T2r 受体。这些钙反应可以被特定的苦味阻断剂抑制，或者通过敲除 G 蛋白亚基 α-味觉素基因而消除。总之，我们的数据强烈表明，生精细胞与口腔中的味蕾细胞和气道中的单个化学感觉细胞一样，利用 T2r 受体来感知环境中的化学物质，这些化学物质可能影响精子行为和受精。
