Insulin receptor substrate-1 pleckstrin homology and phosphotyrosine-binding domains are both involved in plasma membrane targeting.
J Biol Chem
; 276(44): 40795-802, 2001 Nov 02.
Article
en En
| MEDLINE
| ID: mdl-11526109
ABSTRACT
The localization of insulin receptor substrate (IRS) molecules may be responsible for the differential biological activities of insulin and other peptides such as platelet-derived growth factor. The subcellular localization of IRS-1 is controversial, with some reports suggesting association with the cytoskeleton and other studies reporting membrane localization. In this study, we used immunofluorescence microscopy to define the localization of IRS-1. In the basal state, recombinant IRS-1 was localized predominantly in the cytoplasm. In response to insulin, recombinant IRS-1 translocated to the plasma membrane. We have also studied the localization of green fluorescent protein (GFP) fusion proteins. Unlike native IRS-1, a fusion protein containing GFP plus full-length IRS-1 appeared to localize in inclusion bodies. In contrast, when GFP was fused to the N terminus of IRS-1 (i.e. the pleckstrin homology and phosphotyrosine-binding domains), this fusion protein was targeted to the plasma membrane. Mutations of phosphoinositide-binding sites in both the pleckstrin homology and phosphotyrosine-binding domains significantly reduced the ability of Myc-tagged IRS-1 to translocate to the plasma membrane following insulin stimulation. However, these mutations did not cause a statistically significant impairment of tyrosine phosphorylation in response to insulin. This raises the possibility that IRS-1 tyrosine phosphorylation may occur prior to plasma membrane translocation.
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Base de datos:
MEDLINE
Asunto principal:
Fosfoproteínas
/
Proteínas Sanguíneas
/
Fosfotirosina
Límite:
Animals
Idioma:
En
Revista:
J Biol Chem
Año:
2001
Tipo del documento:
Article
País de afiliación:
Estados Unidos