L-plastin: Structure, Regulation, and Roles in Cancer Invasion and in Macrophages

The cytoskeleton consists of 3 filamentous components: intermediate filaments, microtubules, and actin filaments. Actin filaments continuously assemble and disassemble far out of equilibrium to adapt cells in response to external stimuli. Actin filaments organization and dynamic are controlled by a multitude of actin-binding proteins including actin-bundling proteins. L-plastin, expressed abundantly in lymphocytes and monocytes, is an actin-bundling protein that roles in immune defense and in metastatic invasion of cancer cells. The actin-bundling activity of L-plastin is regulated not only by intracellular calcium concentration, but by phosphorylation of Ser5. The actin-bundling activity of L-pastin decreases by increased calcium concentration but is promoted by phosphorylation of Ser5. The morphology changes and motility of cells requires continuous remodeling of actin filaments which demands the sensitive nature of L-plastin to Ca2+-signal, phosphorylation of Ser5, and probably additional regulation. This review briefly describes the structure and regulation of L-plastin, and roles for L-plastin in cancer invasion and in macrophages.

Identification of transcription factor SP-1 upregulating the expression of L-plastin in hormone-independent prostate cancer / 中国病理生理杂志

AIM: To identify the non-steroid transcription factors upregulating the expression of L-plastin in hormone-independent prostate cancer, and partly elucidate the mechanism of hormone-refractory prostate cancer. METHODS: TF SEARCH software was used to analysis the possible binding sites of transcription factors in the 3’ end of L-plastin promoter that had been identified as important part of regulation response elements. Gel shift assay and supershift assay were used to confirm the transcription factors binding the speculated response elements. PCR site-mutagenesis technique was performed to delete the binding site of transcription factor and luciferase activity assay was carried out after deletion of the binding site. RESULTS: SP-1 respond element GGTGGGGCGGGGA located at -54- -41 of L-plastin promoter was identified with the TF SEARCH software. Gel shift assay and supershift assay confirmed that SP-1 was the transcription factor binding to GGTGGGGCGGGGA. Mutant deleted the SP-1 binding-site had low-luciferase activity than that of the naive. CONCLUSION: SP-1 plays an important role in the up-regulation of L-plastin expression in hormone-independent prostate cancer.