Bitter taste receptor T2R14 and autophagy inhibition influence programmed cell death proteomic networks in gingival epithelial cells

Gingival epithelial cells (GECs) form a critical barrier against oral stressors; dysregulated programmed cell death (PCD) may contribute to oral diseases, such as periodontitis and oral cancer. Taste receptor type 2 member 14 (T2R14) is a broadly expressed bitter taste receptor implicated in regulating autophagy and PCD; however, whether it controls multiple PCD pathways through autophagy remains unclear. This study aimed to investigate the roles of T2R14 and autophagy in four PCD pathways in GECs, including autophagy-induced cell death, apoptosis, necroptosis, and ferroptosis. Oral keratinocyte fotofluidic-6 cells were used as a GEC model to study the roles of T2R14 knockout (T2R14-KO), autophagy-related 7 knockdown (ATG7-KD), and the autophagy inhibitor bafilomycin A1 (BAF) in PCD protein expression, using mass spectrometry-based proteomics and pathway-focused bioinformatics analysis. T2R14-KO altered the expression of regulatory proteins involved in autophagy, apoptosis, and necroptosis without substantially affecting their core machineries, but modulated core components of ferroptosis. Thirty-nine proteins, including nine that regulate autophagy, necroptosis, and ferroptosis, were upregulated by BAF but not by ATG7-KD, suggesting that they are candidate autophagy cargoes and that ATG7-KD's effect might be less dependent on autophagy inhibition. T2R14 may modulate crosstalk among autophagy, apoptosis, necroptosis, and ferroptosis. BAF may contribute to autophagy-necroptosis crosstalk via sequestosome 1. Therefore, T2R14 might modulate crosstalk among PCD pathways and more directly influence ferroptosis. Autophagy may simultaneously degrade 39 candidate cargoes, and ATG7-KD might be less dependent on autophagy inhibition for cargo degradation in GECs. These findings could help manipulate GEC death to manage oral diseases.