Structural basis for the function of the Bcr-Abl protein substrate CrkL and human-CrkII as a novel partner for Cyclophilin A
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Jankowski, Wojciech.
Structural basis for the function of the Bcr-Abl protein substrate CrkL and human-CrkII as a novel partner for Cyclophilin A. Retrieved from
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TitleStructural basis for the function of the Bcr-Abl protein substrate CrkL and human-CrkII as a novel partner for Cyclophilin A
Date Created2012
Other Date2012-10 (degree)
Extentxxix, 154 p. : ill.
DescriptionAdaptor proteins are known to play an essential role in assembling protein-protein complexes which result in cellular signal propagation. Crk belongs to a family of adaptor proteins and was originally identified as an oncogene product of the CT10 retrovirus (v-Crk). Cellular homologues of v-Crk include CrkI, CrkII and CrkL. CrkI and CrkII are different splice variants, whereas CrkL is encoded by a distinct gene. Crk proteins contain one Src homology 2 (SH2) and one or two Src homology 3 (SH3) domains. Specific domain organization can assemble and activate a number of different ligands, including Abl. It remains poorly understood why CrkII and CrkL have distinct physiological roles despite showing similar domain structures, high sequence identity, and identical binding partners. Unlike CrkII, CrkL was found to be a key signaling molecule to interact with Bcr-Abl, which is a tyrosine kinase that plays a major role in Chronic Myeloid Leukemia(CML) pathogenesis. The interaction of CrkL with Bcr-Abl and its potent tyrosine phosphorylation (higher as compared to CrkII) is commonly used as a hallmark of Bcr-Abl kinase activity and response to tyrosine kinase inhibitors used in CML treatment. Knowing the differences in 3-dimensional structures between CrkII and CrkL would help to understand how these adaptors alter key signaling partners. However, the structure of CrkL is not available.
Using NMR spectroscopy methodologies complemented by many other biochemical and biophysical techniques, we show that CrkL and phosphorylated CrkL structures are radically different from the corresponding structures of CrkII. The phosphorylation of Tyr221 (CrkII) and Tyr207 (CrkL) by Abl induces intramolecular binding to the SH2 domain, which in the case of phosphorylated CrkII was shown to completely abrogate signal transduction. In phosphorylated CrkL, however, the SH3N domain remains accessible and can form complexes. The data show that CrkL, unlike CrkII, forms a constitutive complex with Abl hence explaining the preference of Bcr-Abl for CrkL over CrkII. The results also highlight how the structural organization of the modular domains in adaptor proteins can control signaling outcome.
In the second part we show that the Gly219−Pro220 motif of CrkII binds into theactive site cleft of CypA. In contrast, CrkL does not contain this GP motif and therefore, is not susceptible to CypA regulation. The interaction between CypA and CrkII occurs both in vitro and in vivo. CypA is recruited to the CrkII phosphorylation site (Tyr221), and delays phosphorylation by Abl. This is a novel role for CypA, which appears to act as a selective switch to modulate the level of phosphorylation of a signaling protein.
NotePh.D.
NoteIncludes bibliographical references
NoteIncludes vita
Noteby Wojciech Jankowski
Genretheses, ETD doctoral
Languageeng
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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