Bruneau N, Lombardo D
INSERM Unité 260, Faculté de Médecine Timone, Marseille, France.
J Biol Chem. 1995 Jun 2;270(22):13524-33. doi: 10.1074/jbc.270.22.13524.
In its fundamental attributes, the secretion pathway of the pancreatic bile salt-dependent lipase (BSDL) followed that described for all enzymes involved in regulated secretion. This route was inhibited by drugs that affect protein synthesis and intracellular transport. In the presence of monensin, BSDL was solely detected in microsome membrane fractions. The association of BSDL with intracellular membranes involved a protein complex, formed by at least two proteins of 94 and 56 kDa. In cells experiencing the metabolic stress due to azetidine-2-carboxylic acid, BSDL was additionally associated with a protein of 46 kDa. Affinity blotting showed that BSDL bound directly to the 94-kDa protein (p94). It was suggested that p94 could be a molecular chaperone, further identified as related to the 94-kDa glucose regulated protein (Grp 94). The membrane-associated BSDL (i.e. BSDL bound to the Grp 94-related p94) was O- and N-glycosylated and consequently appeared released from membranes in the trans-Golgi compartment. Therefore and for the first time, it is suggested that a multiprotein complex including the chaperone Grp 94-related p94 protein may play an essential role in the folding and transport of BSDL. One hypothesis is that the association of BSDL with membrane via the Grp 94-related p94 along its secretion pathway is required for its complete O-glycosylation, which occurs on the extended mucin-like structures present on the C-terminal part of the protein.
在其基本特性方面,胰腺胆汁盐依赖性脂肪酶(BSDL)的分泌途径遵循所有参与调节性分泌的酶所描述的途径。该途径受到影响蛋白质合成和细胞内运输的药物的抑制。在莫能菌素存在的情况下,仅在微粒体膜组分中检测到BSDL。BSDL与细胞内膜的结合涉及一种蛋白质复合物,该复合物由至少两种94 kDa和56 kDa的蛋白质组成。在因氮杂环丁烷-2-羧酸而经历代谢应激的细胞中,BSDL还与一种46 kDa的蛋白质相关联。亲和印迹显示BSDL直接与94 kDa的蛋白质(p94)结合。有人提出p94可能是一种分子伴侣,进一步鉴定为与94 kDa葡萄糖调节蛋白(Grp 94)相关。与膜相关的BSDL(即与Grp 94相关的p94结合的BSDL)进行了O-和N-糖基化,因此似乎在反式高尔基体区室中从膜上释放出来。因此,首次有人提出,包括伴侣蛋白Grp 94相关的p94蛋白在内的多蛋白复合物可能在BSDL的折叠和运输中起重要作用。一种假设是,BSDL在其分泌途径中通过与Grp 94相关的p94与膜结合,这是其完整O-糖基化所必需的,O-糖基化发生在该蛋白质C末端部分存在的延伸的粘蛋白样结构上。