Rab7 is known to function in the autophagy and endocytosis pathways in eukaryocytes and is related to various diseases. We recently reported that Rab7 plays a protective role against acute pancreatitis. However, its physiological function in exocytic cells remains unclear. Therefore, we investigated the role of Rab7 in pancreas-specific Rab7 knockout mice (Rab7^Δpan). Immunofluorescence microscopy revealed that Rab7 colocalized with amylase in pancreatic acinar cells of wild-type mice, but not in Rab7^Δpan mice. Western blotting confirmed Rab7 localization in the zymogen granule (ZG) membranes of wild-type mice. Cholecystokinin (CCK)-stimulated amylase secretion examined using isolated pancreatic acini was similar in Rab7^Δpan and wild-type mice. In contrast, electron microscopy revealed that the diameters of ZGs were shorter and the number of ZGs was larger in the pancreatic acinar cells of Rab7^Δpan mice than in those of wild-type mice. However, the number of ZGs decreased in both Rab7^Δpan and wild-type mice after 24 h of starvation. In addition, the amount of amylase in the pancreas was decreased in both Rab7^Δpan and wild-type mice. These data indicate that Rab7 localized on ZGs plays a crucial role in the maturation of ZGs but not in their autophagy or regulated exocytosis in pancreatic acinar cells.

Rab7 已知在真核细胞的自噬和内吞途径中发挥作用，并与多种疾病相关。我们最近报道 Rab7 对急性胰腺炎具有保护作用。然而，其在胞吐细胞中的生理功能仍不清楚。因此，我们研究了 Rab7 在胰腺特异性 Rab7 敲除小鼠 (Rab7 ^Δpan ) 中的作用。免疫荧光显微镜显示，Rab7 与野生型小鼠的胰腺腺泡细胞中的淀粉酶共定位，但在 Rab7 ^Δpan小鼠中则不然。 Western blotting 证实 Rab7 定位于野生型小鼠的酶原颗粒 (ZG) 膜中。使用分离的胰腺腺泡检查胆囊收缩素 (CCK) 刺激的淀粉酶分泌在 Rab7 ^Δpan和野生型小鼠中相似。相反，电镜观察显示，与野生型小鼠相比，Rab7 ^Δpan小鼠的胰腺腺泡细胞中ZG的直径更短，ZG的数量更多。然而，饥饿 24 小时后，Rab7 ^Δpan和野生型小鼠的 ZG 数量均减少。此外，Rab7 ^Δpan和野生型小鼠胰腺中的淀粉酶量均减少。这些数据表明，定位在 ZG 上的 Rab7 在 ZG 的成熟中发挥着至关重要的作用，但在 ZG 的自噬或胰腺腺泡细胞中调节的胞吐作用中却没有发挥关键作用。