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Impairment of bile salt‐dependent lipase secretion in human pancreatic tumoral SOJ‐6 cells
Author(s) -
Caillol Nathalie,
Pasqualini Eric,
Lloubes Roland,
Lombardo Dominique
Publication year - 2000
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/1097-4644(20001215)79:4<628::aid-jcb120>3.0.co;2-t
Subject(s) - rab , biology , golgi apparatus , cytosol , secretion , microbiology and biotechnology , gene isoform , microsome , endoplasmic reticulum , biochemistry , gene , enzyme , gtpase
Bile salt‐dependent lipase (BSDL) was detected in human SOJ‐6 and rat AR4‐2J pancreatic cells. Whereas AR4‐2J cells actively secreted the enzyme, BSDL was retained within the Golgi compartment of SOJ‐6 cells. Because Rab6 is involved in vesicle transport in the Golgi apparatus and the trans ‐Golgi network, we confirmed the presence of Rab6 in these cells. In rat AR4‐2J cells, Rab6 as well as Rab1A/B and Rab2, partitioned between the cytosol and microsomes. In SOJ‐6 cells Rab1A/B and Rab2 also partitioned between the cytosol and microsomes, but Rab6 was strictly associated with microsome membranes, suggesting a specific defect of Rab6 cycling in human SOJ‐6 cells. The apparent defect of cycling in these cells is not due to the expression of a defective Rab6 since its correct sequence was confirmed. We further demonstrated that AR4‐2J and SOJ‐6 cells express the Rab‐GDIβ and Rab‐GDIα isoforms, respectively. However, the sequence of Rab‐GDIβ, which may be the main form expressed by SOJ‐6 cells, identified a few substitutions located in regions that are essential for Rab‐GDI function. We conclude that the deficient secretion of BSDL by SOJ‐6 cells could be due to the expression of defective Rab‐GDIβ. In spite of the alterations in Rab‐GDIβ, membrane proteins such as CD71 and NHE3 were correctly localized to the cell plasma membrane of SOJ‐6 cells, suggesting that two functional distinct secretory pathway coexist in pancreatic cells. J. Cell. Biochem. 79:628–647, 2000. © 2000 Wiley‐Liss, Inc.