Role of the Ca(2+) channel α(2)δ-1 auxiliary subunit in proliferation and migration of human glioblastoma cells

The overexpression of α(2)δ-1 is related to the development and degree of malignancy of diverse types of cancer. This protein is an auxiliary subunit of voltage-gated Ca(2+) (Ca(V)) channels, whose expression favors the trafficking of the main pore-forming subunit of the channel complex (α(1)) to the plasma membrane, thereby generating an increase in Ca(2+) entry. Interestingly, TLR-4, a protein belonging to the family of toll-like receptors that participate in the inflammatory response and the transcription factor Sp1, have been linked to the progression of glioblastoma multiforme (GBM). Therefore, this report aimed to evaluate the role of the α(2)δ-1 subunit in the progression of GBM and investigate whether Sp1 regulates its expression after the activation of TLR-4. To this end, the expression of α(2)δ-1, TLR-4, and Sp1 was assessed in the U87 human glioblastoma cell line, and proliferation and migration assays were conducted using different agonists and antagonists. The actions of α(2)δ-1 were also investigated using overexpression and knockdown strategies. Initial luciferase assays and Western blot analyses showed that the activation of TLR-4 favors the transcription and expression of α(2)δ-1, which promoted the proliferation and migration of the U87 cells. Consistent with this, overexpression of α(2)δ-1, Sp1, and TLR-4 increased cell proliferation and migration, while their knockdown with specific siRNAs abrogated these actions. Our data also suggest that TLR-4-mediated regulation of α(2)δ-1 expression occurs through the NF-kB signaling pathway. Together, these findings strongly suggest that the activation of TLR-4 increases the expression of α(2)δ-1 in U87 cells, favoring their proliferative and migratory potential, which might eventually provide a theoretical basis to examine novel biomarkers and molecular targets for the diagnosis and treatment of GBM.