ABLIM1, a novel ubiquitin E3 ligase, promotes growth and metastasis of colorectal cancer through targeting IĸBα ubiquitination and activating NF-ĸB signaling

Actin-binding LIM protein 1 (ABLIM1), a member of the LIM-domain protein family, has been reported as a suppressor in several tumors whereas its role in colorectal cancer (CRC) remains unknown. In this study, we find that ABLIM1 is up-regulated in CRC patients and high levels of ABLIM1 predict short disease-free survival time. Knock-down of ABLIM1 in CRC cell lines by lenti-virus leads to inhibited cell proliferation, migration, and invasion capabilities in vitro and impaired growth of tumor xenografts and liver metastasis lesions in vivo, while ABLIM1 overexpression accelerates tumor growth and invasion in vitro. Mechanistically, we uncover that ABLIM1 activates the NF-ĸB/CCL-20 signaling through modulating IĸBα ubiquitination and proteasomal-mediated degradation. Further co-immunoprecipitation, in vivo and in vitro ubiquitination assays reveal ABLIM1 as a novel ubiquitin E3 ligase binding to IĸBα. Interestingly, The E3 ligase catalysis activity of ABLIM1 depends on its 402-778aa rather than its LIM domains and its interaction with IĸBα relies on the HP domain. Our findings delineate the oncogenic role of ABLIM1 in CRC progression and reveal it as a novel E3 ligase targeting IĸBα, providing new insights into the regulation of NF-ĸB signaling in tumors.