MICALL2 as a substrate of ubiquitinase TRIM21 regulates tumorigenesis of colorectal cancer

Background: Molecule interacting with CasL-like protein 2 (MICALL2) is believed to regulate cytoskeleton dynamics, tight junction formation, and neurite outgrowth. However, its biological role and the underlying mechanism in colorectal cancer (CRC) remain largely elusive.

Methods: qRT-PCR, Western blotting and immunohistochemistry assays were used to detect the expression levels of different genes. Next, mass spectrometry, co-immunoprecipitation and immunofluorescence staining were used to detect the interactions of proteins. Furthermore, MTT assay, colony formation assay, wound-healing assays and xenograft tumor models were performed to demonstrate the functions of MICALL2 in CRC. In addition, transcriptome sequencing and Western blotting were conducted to verify the mechanism of MICALL2 in CRC.

Results: We found that both mRNA and protein levels of MICALL2 are up-regulated in colorectal cancer tissues compared with non-tumor tissues and that its overexpression is closely correlated with poor prognosis. Ubiquitin E3 ligase Tripartite motif-containing protein 21 (TRIM21) mediated MICALL2 ubiquitination and proteasome-dependent degradation, negatively correlated with MICALL2 levels, and reversely regulated the tumorigenic activity of MICALL2 in CRC. Functional studies confirmed that MICALL2 promoted colorectal cancer cell growth and migration via the Wnt/β-catenin signaling pathway.

Conclusions: As a substrate of ubiquitinase TRIM21, MICALL2 enhances the growth and migration of colorectal cancer cells and activates the Wnt/β-catenin signaling pathway. Video abstract.