Characterization of Endophilin B1b, a brain-specific membrane-associated lysophosphatidic acid acyl transferase with properties distinct from endophilin A1.
We have characterized mammalian endophilin B1, a novel member of the endophilins and a representative of their B subgroup. The endophilins B show the same domain organization as the endophilins A, which contain an N-terminal domain responsible for lipid binding and lysophosphatidic acid acyl transferase activity, a central coiled-coil domain for oligomerization, a less conserved linker region, and a C-terminal Src homology 3 (SH3) domain. The endophilin B1 gene gives rise to at least three splice variants, endophilin B1a, which shows a widespread tissue distribution, and endophilins B1b and B1c, which appear to be brain-specific. Endophilin B1, like endophilins A, binds to palmitoyl-CoA, exhibits lysophosphatidic acid acyl transferase activity, and interacts with dynamin, amphiphysins 1 and 2, and huntingtin. However, in contrast to endophilins A, endophilin B1 does not bind to synaptojanin 1 and synapsin 1, and overexpression of its SH3 domain does not inhibit transferrin endocytosis. Consistent with this, immunofluorescence analysis of endophilin B1b transfected into fibroblasts shows an intracellular reticular staining, which in part overlaps with that of endogenous dynamin. Upon subcellular fractionation of brain and transfected fibroblasts, endophilin B1 is largely recovered in association with membranes. Together, our results suggest that the action of the endophilins is not confined to the formation of endocytic vesicles from the plasma membrane, with endophilin B1 being associated with, and presumably exerting a functional role at, intracellular membranes.
Modregger
Jan
J
Center for Biochemistry II, Medical Faculty, Joseph-Stelzmann-Strasse 52, University of Cologne, Germany.
Schmidt
Anne A
AA
Ritter
Brigitte
B
Huttner
Wieland B
WB
Plomann
Markus
M
D016475:3T3 Cells; D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D018076:DNA, Complementary; D005227:Fatty Acids / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018076:DNA, Complementary; D005227:Fatty Acids; C498434:Sh3gl2 protein, mouse; C486100:Sh3glb1 protein, mouse; D000217:Acyltransferases; C018764:2-acylglycerophosphate acyltransferase