The International Journal of Biochemistry & Cell Biology 34 (2002) 93 – 102 Identification and characterization of AGTRAP, a human homolog of murine Angiotensin II Receptor-Associated Protein (Agtrap)  Wei Wang a , Yan Huang a , Zongxiang Zhou a,b , Rong Tang a,b , Wei Zhao a , Li Zeng a , Ming Xu a , Chao Cheng a , Shaohua Gu a , Kang Ying a,b , Yi Xie a, *, Yumin Mao a, * a State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Sciences, Fudan Uniersity, Shanghai 200433, People’s Republic of China b United Gene Holdings, Ltd., Shanghai 200092, People’s Republic of China Received 30 April 2001; received in revised form 3 July 2001; accepted 5 July 2001 Abstract Several classes of cytoplasmic proteins have been found to interact specifically with the carboxyl-terminal cytoplasmic region of the angiotensin II type 1 (AT 1 ) receptor to regulate different aspects of AT 1 receptor physiology. The murine Angiotensin II Receptor-Associated Protein (Agtrap) is a new member of them. We have recently cloned a new human gene cDNA that codes for a homolog of the murine Agtrap protein from a human fetal brain cDNA library. The deduced polypeptide product of the cDNA is 22 kDa in size, and its DNA and amino acid sequences are 85 and 77% identical to those of the mouse Agtrap gene, respectively. Hence we have named it the human Angiotensin II Receptor-Associated Protein (AGTRAP) gene. The mRNA of AGTRAP was most abundantly expressed in kidney, heart, pancreas and thyroid. Using the yeast two-hybrid screening of a human fetal brain cDNA library, we have identified a new interaction partner of the human AGTRAP protein, RACK1 (Receptor of Activated Protein C Kinase). The AGTRAP – RACK1 interaction was confirmed by GST fusion protein pull-down assays, co-immunoprecipitation and surface plasmon resonance. We suggest that the AGTRAP – RACK1 interaction may help to recruit signaling complex to the AT 1 receptor to affect AT 1 receptor signaling. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: AGTRAP; Angiotensin II type I receptor; RACK1 www.elsevier.com/locate/ijbcb 1. Introduction The vasopressor hormone angiotensin II (Ang II) plays an important role in the regulation of fluid and salt homeostasis of the cardiovascular system. It can also function as a neuromodulator,  The nucleotide sequence reported in this paper has been submitted to the GenBank/EMBL Database with accession number AF312374. * Corresponding authors. Tel.: +86-21-6564-3573; Fax: +86-21-6564-2502. Tel.: +86-21-5552-0025 (Y. Xie). E-mail address: ymmao@fudan.edu.cn (Y. Mao). 1357-2725/02/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S1357-2725(01)00094-2