This competitive renewal requests continued support for our investigation on ILK, a central component of supramolecular integrin adhesome involved in regulating diverse cellular processes such as cell shape change, migration, and survival. Discovered in 1996, ILK has long been thought to function as a serine- threonine kinase that phosphorylates cytoplasmic tails (CT) of integrin receptors and transmit signals between ECM and actin cytoskeleton. Highly elevated in failing hearts and tumors, ILK has also been pursued as a """"""""hot"""""""" kinase target for therapeutics development. However, our recent structural analysis revealed that ILK contains a severely degraded active site. Extensive biochemical analyses, in parallel with genetic data, corroborated this observation, strongly indicating that ILK is a pseudokinase. Our finding thus challenges a 16-year dogma, signifying a major new direction of the ILK research as indicated by a dozen recent review articles. Our immediate questions are: (i) without catalytic function, how does ILK mediate the integrin-actin communication and other signaling events? (ii) Given the clinical importance of ILK, what might be a new strategy for the ILK- based therapy? In preliminary studies, we found that ILK utilizes two distinct interfaces, one at its N-terminal ankyrin repeat domain (ARD) and the other at the pseudoactive site of the C-terminal kinase-like domain (KLD), to bind adaptors PINCH and Parvin respectively, leading to the formation of a tight heterotrimer (IPP). We further discovered that this ILK-centered heterotrimer binds G-actin and promotes dynamic F-actin assembly. These findings provide exciting clues for unraveling the mechanism of ILK function. In particular, they potentially explai a long-standing puzzle why loss of ILK drastically impairs the actin cytoskeleton and inhibits cell migration. Since ILK also binds to integrin and other signaling molecules, we are entering into a new era for elucidating how ILK may act as a central scaffolding machinery to regulate cytoskeleton remodeling and cell adhesion. In the next funding period, we will rigorously examine this machinery by determining the detailed structural basis of ILK-mediated actin assembly via IPP (Aim1) and elucidate how this actin assembly process is coupled with ECM via a novel integrin-IPP-actin pathway (Aim2). We will further investigate how this pathway may cross-talk with other pathways for cooperative regulation of cell adhesion dynamics (Aim3). Overall, our proposal represents a major programmatic shift for the ILK research. The results will provide a new and comprehensive view of the ILK-mediated signaling and cell adhesion. They may also impact on our understanding of multiple ILK-associated diseases and also re-invigorate strategies for the ILK-targeted therapy.
The heterotrimeric complex between ILK, PINCH, and Parvin proteins (IPP) plays a central role in transmitting information between cell exterior and interior. Dysregulation of this complex has been linked to numerous diseases especially heart failure. Our proposal will elucidate the molecular basis of a novel IPP-mediated pathway linking cell exterior and interior, which may lead to fundamental understanding of cell adhesion and movement at normal and disease states of our body. The study will impact on developing new strategies for treating IPP-associated diseases.
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|Cai, Gang; Zhu, Liang; Chen, Xing et al. (2018) TRAF4 binds to the juxtamembrane region of EGFR directly and promotes kinase activation. Proc Natl Acad Sci U S A 115:11531-11536|
|Liu, Caini; Zhu, Liang; Fukuda, Koichi et al. (2017) The flavonoid cyanidin blocks binding of the cytokine interleukin-17A to the IL-17RA subunit to alleviate inflammation in vivo. Sci Signal 10:|
|Zhu, Liang; Yang, Jun; Bromberger, Thomas et al. (2017) Structure of Rap1b bound to talin reveals a pathway for triggering integrin activation. Nat Commun 8:1744|
|Bledzka, Kamila; Bialkowska, Katarzyna; Sossey-Alaoui, Khalid et al. (2016) Kindlin-2 directly binds actin and regulates integrin outside-in signaling. J Cell Biol 213:97-108|
|Plow, Edward F; Qin, Jun (2015) The role of RIAM in platelets put to a test. Blood 125:207-8|
|Meller, Julia; Rogozin, Igor B; Poliakov, Eugenia et al. (2015) Emergence and subsequent functional specialization of kindlins during evolution of cell adhesiveness. Mol Biol Cell 26:786-96|
|Qin, Jun; Gronenborn, Angela M (2014) Weak protein complexes: challenging to study but essential for life. FEBS J 281:1948-9|
|Murphy, James M; Zhang, Qingwei; Young, Samuel N et al. (2014) A robust methodology to subclassify pseudokinases based on their nucleotide-binding properties. Biochem J 457:323-34|
|Fukuda, Koichi; Bledzka, Kamila; Yang, Jun et al. (2014) Molecular basis of kindlin-2 binding to integrin-linked kinase pseudokinase for regulating cell adhesion. J Biol Chem 289:28363-75|
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