Racz Gabor Z, Perez-Riveros Paola, Adriaansen Janik, Zheng Changyu, Baum Bruce J
Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA.
J Gene Med. 2009 Jul;11(7):580-7. doi: 10.1002/jgm.1340.
Salivary glands have been proposed as target organs for gene therapy. They secrete endogenous, as well as transgenic proteins, in a polarized manner. Transgene-encoded regulated pathway proteins primarily follow the regulated pathway in rat salivary glands and are secreted into saliva in an exocrine manner. Conversely, constitutive pathway proteins generally are secreted more basolaterally and thus follow the endocrine route. In the present study, we studied in vivo the sorting of the mouse immunoglobulin G2b Fc fragment, which is physiologically secreted via the constitutive pathway.
Adenoviral vectors encoding the Fc fragment and human growth hormone were delivered into rat and mouse submandibular glands in vivo to compare their serum-to-saliva distribution. We also compared the intracellular localization of the Fc fragment and growth hormone by confocal microscopy.
We found that the Fc fragment was secreted almost entirely into the bloodstream from rat and mouse submandibular glands via a constitutive or constitutive-like pathway. This sorting behaviour is clearly different from that of transgenic human growth hormone, which is secreted in a regulated pathway, both in neuroendocrine cells and as a transgenic protein from salivary gland cells. We also found that simultaneously expressed human growth hormone and the mouse Fc fragment do not appear to influence each other's sorting behaviour. The Fc fragment showed a primarily basal localization, whereas growth hormone showed an apical localization, in rat submandibular gland acinar cells.
The results obtained in the present study indicate that the mouse Fc fragment is a useful model protein for examining the basolateral versus apical secretory pathways employed by transgenic secretory proteins in salivary glands.
唾液腺已被提议作为基因治疗的靶器官。它们以极化方式分泌内源性蛋白质以及转基因蛋白。转基因编码的调节途径蛋白在大鼠唾液腺中主要遵循调节途径，并以外分泌方式分泌到唾液中。相反，组成型途径蛋白通常更多地从基底外侧分泌，因此遵循内分泌途径。在本研究中，我们在体内研究了小鼠免疫球蛋白G2b Fc片段的分选，该片段通过组成型途径进行生理性分泌。
将编码Fc片段和人生长激素的腺病毒载体体内递送至大鼠和小鼠下颌下腺，以比较它们在血清和唾液中的分布。我们还通过共聚焦显微镜比较了Fc片段和生长激素的细胞内定位。
我们发现Fc片段几乎完全通过组成型或类组成型途径从大鼠和小鼠下颌下腺分泌到血液中。这种分选行为与转基因人生长激素明显不同，转基因人生长激素在神经内分泌细胞中以及作为唾液腺细胞中的转基因蛋白以调节途径分泌。我们还发现同时表达的人生长激素和小鼠Fc片段似乎不会相互影响彼此的分选行为。在大鼠下颌下腺腺泡细胞中，Fc片段主要定位于基底侧，而生长激素定位于顶端。
本研究获得的结果表明，小鼠Fc片段是一种有用的模型蛋白，可用于研究唾液腺中转基因分泌蛋白所采用的基底外侧与顶端分泌途径。
