MCU regulates metastasis of oral squamous cell carcinoma cells by maintaining mitochondrial calcium homeostasis through LETM1

Abstract:

Objective To investigate the role of mitochondrial calcium uniporter（MCU） and leucine zipper/EF hand-containing transmembrane-1 （LETM1） in regulating mitochondrial calcium homeostasis and its effect on the metastasis of oral squamous cell carcinoma cells.Methods Oral squamous cell carcinoma CAL-27 cell line was selected as the research objects. MCU lentiviral interference vector and overexpression plasmid were constructed. LETM1 siRNA interference sequence was synthesized. Cell scratch test and Transwell cell invasion test were used to detect the effect of MCU expression level on the invasion and migration of CAL-27 cells. Intracellular calcium fluorescent probe（Fluo-4 AM ） and JC-1 mitochondrial membrane potential assay were used to detect the effect of MCU expression level on intracellular calcium concentration and mitochondrial membrane potential of CAL-27 cells. The expression levels of MCU，LETM1 and epithelial-mesenchymal transition （EMT）-related proteins in CAL-27 cells were detected by immunofluorescence and Western blot.Results Migration and invasion of CAL-27 cells were promoted by overexpression of MCU. Migration and invasion of CAL-27 cells were significantly inhibited in MCU silencing group and MCU overexpression combined with LETM1 siRNA interference group（F=45.302，1 300.246； all P>0.05）. The intracellular calcium fluorescence intensity and mitochondrial membrane potential were significantly increased in MCU overexpression group，and significantly decreased in MCU silencing group and MCU overexpression combined with LETM1 siRNA interference group（F=75.585，141.767；all P<0.01）. The protein expression levels of MCU，LETM1，N-cadherin and Vimentin in MCU overexpression group were significantly increased，while the protein expression level of E-cadherin was significantly decreased. The protein expression levels of MCU，LETM1，N-cadherin and Vimentin in MCU silencing group were significantly lower than those in other treatment groups，while the protein expression level of E-cadherin was significantly increased（all P<0.01）.Conclusion MCU can regulate the expression of LETM1 and EMT markers. Interference with LETM1 can block MCU up-regulation of mitochondrial calcium concentration and mitochondrial membrane potential and reduce the invasion and migration of oral squamous cell carcinoma cells.