This Article Full Text Full Text (PDF) All Versions of this Article: 102/7/840    most recent CIRCRESAHA.107.168153v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Google Scholar Articles by Min, W. Articles by Chen, H. PubMed PubMed Citation Articles by Min, W. Articles by Chen, H. Related Collections Apoptosis Cell signalling/signal transduction Endothelium/vascular type/nitric oxide

(Circulation Research. 2008;102:840.)
© 2008 American Heart Association, Inc.

Molecular Medicine

AIP1 Recruits Phosphatase PP2A to ASK1 in Tumor Necrosis Factor–Induced ASK1-JNK Activation

Wang Min, Yan Lin, Shibo Tang, Luyang Yu, Haifeng Zhang, Ting Wan, Tricia Luhn, Haian Fu, Hong Chen

From the Interdepartmental Program in Vascular Biology and Therapeutics (W.M., Y.L., L.Y., H.Z., T.W., H.C.), Department of Pathology, Yale University School of Medicine, New Haven, Conn; State Key Laboratory of Ophthalmology (S.T., T.W.), Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, China; and Department of Pharmacology (T.L., H.F.), Emory University, Atlanta, Ga.

Correspondence to Dr. Wang Min, Vascular Biology and Therapeutics Program and Department of Pathology, Yale University School of Medicine, 10 Amistad St, New Haven, CT 06520. E-mail wang.min{at}yale.edu

Previously we have shown that AIP1 (apoptosis signal-regulating kinase [ASK]1-interacting protein 1), a novel member of the Ras-GAP protein family, facilitates dephosphorylation of ASK1 at pSer967 and subsequently 14-3-3 release from ASK1, leading to enhanced ASK1-JNK signaling. However, the phosphatase(s) responsible for ASK1 dephosphorylation at pSer967 has not been identified. In the present study, we identified protein phosphatase (PP)2A as a potential phosphatase in vascular endothelial cells (ECs). Tumor necrosis factor (TNF)-induced dephosphorylation of ASK1 pSer967 in ECs was blocked by PP2A inhibitor okadaic acid. Overexpression of PP2A catalytic subunit induced dephosphorylation of ASK1 pSer967 and activation of c-Jun N-terminal kinase (JNK). In contrast, a catalytic inactive form of PP2A or PP2A small interfering RNA blunted TNF-induced dephosphorylation of ASK1 pSer967 and activation of JNK without effects on NF-B activation. Whereas AIP1, via its C2 domain, binds to ASK1, PP2A binds to the GAP domain of AIP1. Endogenous AIP1-PP2A complex can be detected in the resting state, and TNF induces a complex formation of AIP1-PP2A with ASK1. Furthermore, TNF-induced association of PP2A with ASK1 was diminished in AIP1-knockdown ECs, suggesting a critical role of AIP1 in recruiting PP2A to ASK1. TNF-signaling molecules TRAF2 and RIP1, known to be in complex with AIP1 and activate AIP1 by phosphorylating AIP1 at Ser604, are critical for TNF-induced ASK1 dephosphorylation. Finally, PP2A and AIP1 cooperatively induce activation of ASK1-JNK signaling and EC apoptosis, as demonstrated by both overexpression and small interfering RNA knockdown approaches. Taken together, our data support a critical role of PP2A-AIP1 complex in TNF-induced activation of ASK1-JNK apoptotic signaling.

Key Words: AIP1/DAB2IP • ASK1 • TNF • phosphatase • 14-3-3