Arrestin 1 (Phospho-Ser412) ELISA Kit

During acute rejection, numerous pro-inflammatory and cytotoxic monocytes accumulate in the vasculature of experimental renal allografts. Arrestins (ARRBs) are cellular regulators of inflammation, but nothing is known about their expression during rejection. Intravascular mononuclear graft leukocytes were isolated 4 days after kidney transplantation. ARRB1 and ARRB2 mRNA expression was reduced in blood leukocytes from allografts undergoing acute rejection, whereas on the protein level only ARRB2 was changed. Flow cytometry and confocal microscopy revealed ARRB1 and ARRB2 expression by monocytes and T cells, with a selective decrease in ARRB2 expression in monocytes during acute rejection. I-kappa B directly interacted with ARRB2 and the levels of both proteins strongly correlated. Concomitantly, the mRNA expression of NF-kappa B targeted genes increased. Our results suggest that activation of blood monocytes in renal isografts is dampened by high ARRB2 levels. During acute rejection, ARRB2 levels are reduced and classical monocyte activation is enabled via NF-kappa B activation. (C) 2010 Elsevier GmbH. All rights reserved.

We report that oxytocin (Oxt) receptors (Oxtrs), on stimulation by the ligand Oxt, translocate into the nucleus of osteoblasts, implicating this process in the action of Oxt on osteoblast maturation. Sequential immunocytochemistry of intact cells or isolated nucleoplasts stripped of the outer nuclear membrane showed progressive nuclear localization of the Oxtr; this nuclear translocation was confirmed by monitoring the movement of Oxtr-EGFP as well as by immunogold labeling. Nuclear Oxtr localization was conclusively shown by Western immunoblotting and MS of nuclear lysate proteins. We found that the passage of Oxtrs into the nucleus was facilitated by successive interactions with beta-arrestins (Arrbs), the small GTPase Rab5, importin-beta (Kpnb1), and transportin-1 (Tnpo1). siRNA-mediated knockdown of Arrb1, Arrb2, or Tnpo1 abrogated Oxt-induced expression of the osteoblast differentiation genes osterix (Sp7), Atf4, bone sialoprotein (Ibsp), and osteocalcin (Bglap) without affecting Erk phosphorylation. Likewise and again, without affecting pErk, inhibiting Arrb recruitment by mutating Ser rich clusters of the nuclear localization signal to Ala abolished nuclear import and Oxtr-induced gene expression. These studies define a previously unidentified mechanism for Oxtr action on bone and open possibilities for direct transcriptional modulation by nuclear G protein-coupled receptors.