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Constitutive GDP/GTP exchange and secretion-dependent GTP hydrolysis activity for Rab27 in platelets.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2006 Sep 29; Vol. 281 (39), pp. 28657-65. Date of Electronic Publication: 2006 Jul 31. - Publication Year :
- 2006
-
Abstract
- We have previously demonstrated that Rab27 regulates dense granule secretion in platelets. Here, we analyzed the activation status of Rab27 using the thin layer chromatography method analyzing nucleotides bound to immunoprecipitated Rab27 and the pull-down method quantifying Rab27 bound to the GTP-Rab27-binding domain (synaptotagmin-like protein (Slp)-homology domain) of its specific effector, Slac2-b. We found that Rab27 was predominantly present in the GTP-bound form in unstimulated platelets due to constitutive GDP/GTP exchange activity. The GTP-bound Rab27 level drastically decreased due to enhanced GTP hydrolysis activity upon granule secretion. In permeabilized platelets, increase of Ca(2+) concentration induced dense granule secretion with concomitant decrease of GTP-Rab27, whereas in non-hydrolyzable GTP analogue GppNHp (beta-gamma-imidoguanosine 5'-triphosphate)-loaded permeabilized platelets, the GTP (GppNHp)-Rab27 level did not decrease upon the Ca(2+)-induced secretion. These data suggested that GTP hydrolysis of Rab27 was not necessary for inducing the secretion. Taken together, Rab27 is maintained in the active status in unstimulated platelets, which could function to keep dense granules in a preparative status for secretion.
- Subjects :
- Animals
Calcium metabolism
Humans
Hydrolysis
Nucleotides chemistry
Protein Binding
Protein Structure, Tertiary
Rats
Time Factors
rab27 GTP-Binding Proteins
Adaptor Proteins, Signal Transducing chemistry
Blood Platelets metabolism
Guanosine Diphosphate chemistry
Guanosine Triphosphate chemistry
rab GTP-Binding Proteins chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 281
- Issue :
- 39
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 16880209
- Full Text :
- https://doi.org/10.1074/jbc.M603227200