| Autor: |
Williams, Alison G., Woolkalis, Marilyn J., Poncz, Mortimer, Manning, David R., Gewirtz, Alan M., Brass, Lawrence F. |
| Zdroj: |
Blood; August 1990, Vol. 76 Issue: 4 p721-730, 10p |
| Abstrakt: |
Guanine nucleotide-binding regulatory proteins, or G proteins, mediate the interaction of agonist receptors on the platelet surface with phospholipase C and adenylyl cyclase. To better understand this process, we have used several approaches to identify which G proteins are present in platelets, normal human megakaryocytes, and human erythroleukemia (HEL) cells, a leukemic cell line with megakaryocytic features. Because platelet and HEL cell responses to thrombin are inhibited by pertussis toxin, we have focused upon the members of the Gifamily, whose α subunits can be ADP-ribosylated by that toxin. Western blots with antisera specific for Giαdemonstrated the presence in both platelets and HEL cells of the three best-described forms of this protein: Giα1, Giα2, and Giα3. Based upon immunoprecipitation studies with [35S]-methionine-labeled HEL cells, their relative abundance appears to be Giα2> Giα3> Giα1. A HEL cell cDNA library screened with the Giαantisera produced clones encoding Giα2and Giα3that had sequences similar to those reported from other sources. Giα-specific probes created from these cDNA clones confirmed the presence of mRNA encoding Giα2and Giα3in both platelets (by Northern blotting) and megakaryocytes (by in situ hybridization). Thus the pertussis toxin substrates that have previously been detected in platelets and HEL cells are shown to be members of the Giαfamily, all of which are candidates for interaction with receptors for thrombin and other agonists. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
