Identification of glyceraldehyde-3-phosphate dehydrogenase as a Ca2+-dependent fusogen in human neutrophil cytosol.
The membrane fusion events observed during neutrophil degranulation are important aspects of the immunoregulatory system. In an attempt to understand the regulation of granule-plasma membrane fusion, we have begun characterizing human neutrophil cytosol for fusion activity, finding that 50% of the fusogenic activity could be attributed to members of the annexin family of proteins. The major non-annexin fusion activity (25% of the total cytosolic activity) was enriched by ion exchange chromatography after depletion of annexins by Ca2+-dependent phospholipid affinity chromatography. The fusion activity co-purified with a 10,14-kDa dimer identified as leukocyte L1 (which was non-fusogenic), along with an approximately 36-kDa protein. This protein was identified as glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by amino-terminal sequencing, and the fusion activity was verified using commercially available GAPDH. GAPDH may play an important role in degranulation because it is as potent as annexin I on a mass basis and may constitute up to 25% of the total cytosolic fusion activity of the neutrophil.
Hessler
R J
RJ
Department of Pediatrics, University of Michigan, Ann Arbor, USA.
Blackwood
R A
RA
Brock
T G
TG
Francis
J W
JW
Harsh
D M
DM
Smolen
J E
JE
D017305:Annexin A1 / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D019281:Dimerization; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D006801:Humans; D007700:Kinetics; D008081:Liposomes; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology*; D008970:Molecular Weight; D009504:Neutrophils / Q000201:enzymology*
D017305:Annexin A1; D008081:Liposomes; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D002118:Calcium