Bruneau N, Lombardo D, Bendayan M
Département de Pathologie et Biologie Cellulaire, Faculté de Médecine, Université de Montréal, Montréal, Quebec, H3C 3J7 Canada.
J Cell Sci. 1998 Sep;111 ( Pt 17):2665-79. doi: 10.1242/jcs.111.17.2665.
In previous studies on the AR4-2J cell line, we have shown that secretion of bile salt-dependent lipase (BSDL) involves a multiprotein complex, including a protein of 94 kDa (p94) that is immunologically related to the chaperone Grp94, which seems to play essential roles in the folding process of BSDL. Combined biochemical and immunocytochemical investigations were carried out to study the secretion of BSDL by normal pancreatic cells and its transport to the small intestine where this enzyme is thought to exert its physiological function. Both BSDL and Grp94 antigenic sites were localized and found to be associated all along the pancreatic acinar cell secretory pathway. Grp94 and BSDL remain associated from leaving the pancreas until arriving at the intestinal lumen. In pancreatic juice, both proteins appear as a complex of high molecular mass (180 kDa) containing at least one each of p94 and BSDL molecules, interacting by hydrophobic forces. At the intestinal level, associated Grp94 and BSDL were detected on microvilli and in the endosomal compartment of enterocytes. The BSDL mRNA, however, was not expressed by the intestinal mucosa. The pancreatic Grp94-BSDL complex was internalized through the endosomal compartment of enterocytes. Finally, the two proteins dissociated in this compartment and BSDL, but not Grp94, was transferred to the basolateral membrane.
在之前对AR4-2J细胞系的研究中，我们已经表明，胆汁盐依赖性脂肪酶（BSDL）的分泌涉及一种多蛋白复合物，其中包括一种94 kDa的蛋白（p94），它在免疫学上与伴侣蛋白Grp94相关，而Grp94似乎在BSDL的折叠过程中发挥着重要作用。我们进行了生物化学和免疫细胞化学联合研究，以探讨正常胰腺细胞中BSDL的分泌及其向小肠的转运，因为这种酶被认为在小肠发挥其生理功能。BSDL和Grp94的抗原位点均被定位，并且发现它们在胰腺腺泡细胞分泌途径中全程都有关联。从离开胰腺直到到达肠腔，Grp94和BSDL一直保持关联。在胰液中，这两种蛋白均以高分子质量（180 kDa）的复合物形式出现，该复合物至少包含一个p94分子和一个BSDL分子，二者通过疏水作用力相互作用。在肠道水平，在微绒毛和肠上皮细胞的内体区室中检测到了相关联的Grp94和BSDL。然而，肠黏膜并不表达BSDL mRNA。胰腺Grp94-BSDL复合物通过肠上皮细胞的内体区室被内化。最后，这两种蛋白在该区室中解离，并且BSDL（而非Grp94）被转运至基底外侧膜。
