The Matricellular Protein Cyr61 Signaling Axis in Arterial Restenosis

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Vascular smooth muscle cell (SMC) migration is a critical event in the arterial remodeling in restenosis following angioplasty and stenting. Despite recent advances in drug-eluting technology, arterial restenosis remains a challenging complication. In order to develop innovative therapeutic approaches, discovery of novel regulatory molecules and mechanisms of restenosis is needed. Substantial evidence has shown that platelet- derived growth factor (PDGF) plays a prominent role in SMC migration into the intima following vascular injury. Our recent publication revealed that de novo matricellular protein Cyr61 (CCN1) is the key molecule mediating the PDGF-induced SMC migration via an “outside-in” signaling route through its interaction with integrins α6β1 and αvβ3, which leads to intracellular focal adhesion kinase (FAK) activation. This suggests a Cyr61 signaling axis in arterial restenosis. Interestingly, we also recently observed high levels of Cyr61 expression in mouse angioplasty guidewire-induced femoral arterial lesions. To pursue the role and novel signaling components of the Cyr61 axis in arterial restenosis, we explored an array of protein kinase activation in the polarized leading edge of SMCs using a novel pseudopodium isolation approach. Excitingly, our preliminary data revealed the following findings: PDGF induces activation of a novel pseudopodium-enriched atypical kinase 1 (PEAK1), which is localized in the polarized leading edge of SMCs; knockdown of Cyr61 blocks PDGF-induced PEAK1 activation; depletion of PEAK1 blocks PDGF-induced SMC migration; and PDGF-induced phosphorylated PEAK1 (p-PEAK1) interacts with p-FAK in SMCs. Importantly, we observed that Cyr61 levels and PEAK1 activation are robustly induced in guidewire-induced mouse femoral arterial lesions. Furthermore, both Cyr61 and p-PEAK1 localize in lesion SMCs but not in tunica media SMCs. These data strongly suggest that Cyr61 and the novel pseudopodium kinase PEAK1 play crucial roles in injury-induced arterial restenosis. Based on these new observations, we hypothesize that the Cyr61-α6β1/αvβ3-p-PEAK1-p-FAK mediates injury-induced SMC migration and that Cyr61 and p-PEAK1 control vascular remodeling in arterial restenosis. Our hypothesis will be tested in the following specific aims. Aim 1: Determine how p-PEAK1 interacts with p-FAK in the PDGF pathway, identify the inhibitory peptides serving as therapeutic targets, and examine the key role of Cyr61 on the activation of intracellular cascades using novel Cyr61 null SMCs from our recently created SMC-specific Cyr61 KO mice. Aim 2: Explore the possible complex formation between α6β1 and αvβ3 in PDGF-induced Cyr61 pathway and determine the consequent activation of the intracellular molecules using SMCs derived from innovative Cyr61dm/dm, Cyr61D125A, and SMC-specific Cyr61-/- mice. Aim 3: Determine the role of Cyr61 and novel tyrosine kinase PEAK1 in angioplasty-induced vascular remodeling using three innovative Cyr61 genetic models Cyr61dm/dm, Cyr61D125A, and SMC Cyr61 KO mice. The proposed studies are expected to identify novel targets for prevention and treatment of arterial restenosis.