Nuclear localization of bradykinin B2 receptors reflects binding to the nuclear envelope protein lamin C

The mechanism of action of bradykinin (BK), a pro inflammatory mediator, is thought to be mediated by specific cell surface membrane bradykinin B-2 receptors. Some evidence suggests that there are both intracellular and nuclear bradykinin B-2 receptors. This study identified proteins that interact with the C-terminus of the bradykinin B-2 receptor (in particular, the nuclear membrane protein lamin C), using the yeast two hybrid system. The motif of the C-terminal domain (CT) mutant 303-320 in bradykinin B2 receptor was identified as a lamin C protein binding motif. immunohistochemistry revealed colocalization of FLAG- bradykinin B-2 receptor with HA-lamin C in the nucleus of HEK 293T cells. in situ proximity ligation assay (PLA) showed that FLAG-bradykinin B-2 receptor formed heterodimers with HA-lamin C in the nucleus. in addition, live cell fluorescence imaging showed that bradykinin B-2 receptor-EGFP was located in the nucleus and co-localized with HcRed-lamin C. Interestingly, neither BK addition nor bradykinin B-2 receptor CT mutation reduced the binding to lamin C or changed the distribution of bradykinin B-2 receptor. Taken together, these findings demonstrate that bradykinin B-2 receptor-lamin C heterodimers form in the nucleus independent of BK stimulation and CT mutation. We propose that heterodimerization of bradykinin B-2 receptor with lamin C is essential to nuclear localization of bradykinin B-2 receptor and plays an important role in cell signaling and function. (C) 2013 Elsevier B.V. All tights reserved