TY - JOUR
T1 - Taxol normalizes the impaired agonist-induced β2-adrenoceptor internalization in splenocytes from GRK2+/- mice
AU - Vroon, Anne
AU - Lombardi, Maria Stella
AU - Kavelaars, Annemieke
AU - Heijnen, Cobi J.
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2007/3/29
Y1 - 2007/3/29
N2 - G protein-coupled receptor kinase 2 (GRK2) is involved in the agonist-induced desensitization of β2-adrenoceptors. In addition, GRK2 is capable of binding and phosphorylating tubulin. Interestingly, microtubule dynamics profoundly affect agonist-induced internalization of β2-adrenoceptors. Here, we analyzed agonist-induced β2-adrenoceptor internalization and signaling in splenocytes from GRK2+/- mice that have a ∼ 50% lower level of GRK2 protein compared to wild type (WT) mice. In addition, we investigated the role of microtubule stability in these processes. Splenocytes from GRK2+/- mice express ∼ 50% less β2-adrenoceptors on the cell surface and show impaired agonist-induced β2-adrenoceptor internalization. Disruption of microtubules using colchicine reduces agonist-induced β2-adrenoceptor internalization in cells from WT, but not in cells from GRK2+/- mice. Importantly, increasing tubulin stability by taxol almost completely restores the defective agonist-induced β2-adrenoceptor internalization in cells from GRK2+/- animals, without affecting WT cells. Despite lower surface receptor numbers, cells of GRK2+/- mice show normal β2-adrenoceptor agonist-induced cAMP responses. Although interfering with microtubule stability has major effects on agonist-induced receptor internalization in GRK2+/- cells, microtubule dynamics do not influence cAMP responses. Our data suggest that cells with low GRK2 adapt to the lower GRK2 level by decreasing the number of β2-adrenoceptors on the cell surface. In addition, the cellular GRK2 level determines the extent of agonist-induced β2-adrenoceptor internalization via a mechanism involving microtubule stability. Importantly, however, normalization of agonist-induced receptor internalization by taxol is not sufficient to alter receptor signaling.
AB - G protein-coupled receptor kinase 2 (GRK2) is involved in the agonist-induced desensitization of β2-adrenoceptors. In addition, GRK2 is capable of binding and phosphorylating tubulin. Interestingly, microtubule dynamics profoundly affect agonist-induced internalization of β2-adrenoceptors. Here, we analyzed agonist-induced β2-adrenoceptor internalization and signaling in splenocytes from GRK2+/- mice that have a ∼ 50% lower level of GRK2 protein compared to wild type (WT) mice. In addition, we investigated the role of microtubule stability in these processes. Splenocytes from GRK2+/- mice express ∼ 50% less β2-adrenoceptors on the cell surface and show impaired agonist-induced β2-adrenoceptor internalization. Disruption of microtubules using colchicine reduces agonist-induced β2-adrenoceptor internalization in cells from WT, but not in cells from GRK2+/- mice. Importantly, increasing tubulin stability by taxol almost completely restores the defective agonist-induced β2-adrenoceptor internalization in cells from GRK2+/- animals, without affecting WT cells. Despite lower surface receptor numbers, cells of GRK2+/- mice show normal β2-adrenoceptor agonist-induced cAMP responses. Although interfering with microtubule stability has major effects on agonist-induced receptor internalization in GRK2+/- cells, microtubule dynamics do not influence cAMP responses. Our data suggest that cells with low GRK2 adapt to the lower GRK2 level by decreasing the number of β2-adrenoceptors on the cell surface. In addition, the cellular GRK2 level determines the extent of agonist-induced β2-adrenoceptor internalization via a mechanism involving microtubule stability. Importantly, however, normalization of agonist-induced receptor internalization by taxol is not sufficient to alter receptor signaling.
KW - G protein-coupled receptor kinase 2
KW - Microtubules
KW - Receptor internalization
KW - Tubulin
KW - cAMP
KW - β-adrenoceptor
UR - http://www.scopus.com/inward/record.url?scp=33847246808&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33847246808&partnerID=8YFLogxK
U2 - 10.1016/j.ejphar.2007.01.007
DO - 10.1016/j.ejphar.2007.01.007
M3 - Article
C2 - 17303111
AN - SCOPUS:33847246808
SN - 0014-2999
VL - 560
SP - 9
EP - 16
JO - European Journal of Pharmacology
JF - European Journal of Pharmacology
IS - 1
ER -