Differential subcellular localization of endogenous and transfected soluble epoxide hydrolase in mammalian cells: evidence for isozyme variants

Endogenous, constitutive soluble epoxide hydrolase in mice 3T3 cells was lo calized via immunofluorescence microscopy exclusively in peroxisomes, where as transiently expressed mouse soluble epoxide hydrolase (from clofibrate-t reated liver) accumulated only in the cytosol of 3T3 and HeLa cells. When t he C-terminal Ile of mouse soluble epoxide hydrolase was mutated to generat e a prototypic putative type 1 PTS (-SKI to -SKL), the enzyme targeted to p eroxisomes. The possibility that soluble epoxide hydrolase-SKI was sorted s lowly to peroxiosmes from the cytosol was examined by stably expressing rat soluble epoxide hydrolase-SKI appended to the green fluorescent protein. G reen fluorescent protein soluble epoxide hydrolase-SKI was strictly cytosol ic, indicating that -SKI was not a temporally inefficient putative type 1 P TS, Import of soluble epoxide hydrolase-SKI into peroxisomes in plant cells revealed that the context of -SKI on soluble epoxide hydrolase was targeti ng permissible, These results show that the C-terminal -SKI is a non-functi onal putative type 1 PTS on soluble epoxide hydrolase and suggest the exist ence of distinct cytosolic and peroxisomal targeting variants of soluble ep oxide hydrolase in mouse and rat. (C) 1999 Federation of European Biochemic al Societies.