The intracellular translocation of the components of the fibroblast growth factor 1 release complex precedes their assembly prior to export.
The release of signal peptideless proteins occurs through nonclassical export pathways and the release of fibroblast growth factor (FGF)1 in response to cellular stress is well documented. Although biochemical evidence suggests that the formation of a multiprotein complex containing S100A13 and Synaptotagmin (Syt)1 is important for the release of FGF1, it is unclear where this intracellular complex is assembled. As a result, we employed real-time analysis using confocal fluorescence microscopy to study the spatio-temporal aspects of this nonclassical export pathway and demonstrate that heat shock stimulates the redistribution of FGF1 from a diffuse cytosolic pattern to a locale near the inner surface of the plasma membrane where it colocalized with S100A13 and Syt1. In addition, coexpression of dominant-negative mutant forms of S100A13 and Syt1, which both repress the release of FGF1, failed to inhibit the stress-induced peripheral redistribution of intracellular FGF1. However, amlexanox, a compound that is known to attenuate actin stress fiber formation and FGF1 release, was able to repress this process. These data suggest that the assembly of the intracellular complex involved in the release of FGF1 occurs near the inner surface of the plasma membrane and is dependent on the F-actin cytoskeleton.
Center for Molecular Medicine, Maine Medical Center Research Institute, 81 Research Drive, Scarborough, ME 04074, USA.
Igor
I
Prudovsky
Cinzia
C
Bagala
Francesca
F
Tarantini
Anna
A
Mandinova
Raffaella
R
Soldi
Stephen
S
Bellum
Thomas
T
Maciag
D016475:3T3 Cells; D000818:Animals; D002135:Calcium-Binding Proteins; D016220:Fibroblast Growth Factor 1 / Q000737:chemistry / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D009418:S100 Proteins / Q000737:chemistry / Q000378:metabolism; D050863:Synaptotagmin I; D050857:Synaptotagmins
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D009418:S100 Proteins; C511524:S100a13 protein, mouse; D050863:Synaptotagmin I; C494311:Syt1 protein, mouse; D016220:Fibroblast Growth Factor 1; D050857:Synaptotagmins