Biochem J. 2012 Jul 1;445(1):29-38. doi: 10.1042/BJ20120471.
Homers regulate calcium entry and aggregation in human platelets: a role for Homers in the association between STIM1 and Orai1.
Jardin, I., Albarran, L., Bermejo, N., Salido, G. M., Rosado, J. A.,
["Department of Physiology, Cellular Physiology Research Group, University of Extremadura, 10003 Caceres, Spain."]
["Department of Physiology, Cellular Physiology Research Group, University of Extremadura, 10003 Caceres, Spain."]
Homer is a family of cytoplasmic adaptor proteins that play different roles in cell function, including the regulation of G-protein-coupled receptors. These proteins contain an Ena (Enabled)/VASP (vasodilator-stimulated phosphoprotein) homology 1 domain that binds to the PPXXF sequence motif, which is present in different Ca(2)(+)-handling proteins such as IP3 (inositol 1,4,5-trisphosphate) receptors and TRPC (transient receptor potential canonical) channels. In the present study we show evidence for a role of Homer proteins in the STIM1 (stromal interaction molecule 1)-Orai1 association, as well as in the TRPC1-IP3RII (type II IP3 receptor) interaction, which might be of relevance in platelet function. Treatment of human platelets with thapsigargin or thrombin results in a Ca(2)(+)-independent association of Homer1 with TRPC1 and IP3RII. In addition, thapsigargin and thrombin enhanced the association of Homer1 with STIM1 and Orai1 in a Ca(2)(+)-dependent manner. Interference with Homer function by introduction of the synthetic PPKKFR peptide into cells, which emulates the proline-rich sequences of the PPXXF motif, reduced STIM1-Orai1 and TRPC1- IP3RII associations, as compared with the introduction of the inactive PPKKRR peptide. The PPKKFR peptide attenuates thrombin-evoked Ca(2)(+) entry and the maintenance of thapsigargin-induced store-operated Ca(2)(+) entry. Finally, the PPKKFR peptide attenuated thrombin-induced platelet aggregation. The findings of the present study support an important role for Homer proteins in thrombin-stimulated platelet function, which is likely to be mediated by the support of agonist-induced Ca(2)(+) entry.
PMID: 22506990
 Screening
Validation: In vitro validation
Validation: In vivo validation
Characterization
Functional consequence
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Validation: In vivo validation
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| Assay with endogenous proteins | Assay with overexpressed proteins | Reference | ||||||||
| Cell or tissue | Cell or tissue | TRP channel construct | Interactor construct | |||||||
| TRP channel | Interactor | Method | Species | Region | Species | Region | ||||
| TRPC1 |
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Homer-1 | Co-immunoprecipitation | Human platelets | 22506990 | |||||
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
:
click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)