• Shiori Haga, Norio Yamamoto, Chikako Nakai-Murakami, Yoshiaki Osawa, Kenzo Tokunaga, Tetsutaro Sata, Naoki Yamamoto, Takehiko Sasazuki, and Yukihito Ishizaka.
• Department of Intractable Diseases, International Medical Center of Japan, 162-8655 Tokyo, Japan.
• Proc. Natl. Acad. Sci. U.S.A. 2008 Jun 3; 105 (22): 7809-14.

AbstractSevere acute respiratory syndrome coronavirus (SARS-CoV) is a high-risk infectious pathogen. In the proposed model of respiratory failure, SARS-CoV down-regulates its receptor, angiotensin-converting enzyme 2 (ACE2), but the mechanism involved is unknown. We found that the spike protein of SARS-CoV (SARS-S) induced TNF-alpha-converting enzyme (TACE)-dependent shedding of the ACE2 ectodomain. The modulation of TACE activity by SARS-S depended on the cytoplasmic domain of ACE2, because deletion mutants of ACE2 lacking the carboxyl-terminal region did not induce ACE2 shedding or TNF-alpha production. In contrast, the spike protein of HNL63-CoV (NL63-S), a CoV that uses ACE2 as a receptor and mainly induces the common cold, caused neither of these cellular responses. Intriguingly, viral infection, judged by real-time RT-PCR analysis of SARS-CoV mRNA expression, was significantly attenuated by deletion of the cytoplasmic tail of ACE2 or knock-down of TACE expression by siRNA. These data suggest that cellular signals triggered by the interaction of SARS-CoV with ACE2 are positively involved in viral entry but lead to tissue damage. These findings may lead to the development of anti-SARS-CoV agents.

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