HDLBP Promotes Glycolysis and CD8+ T Cell Exhaustion in Lung Adenocarcinoma by Stabilizing GJB2 RNA.

Abstract

Gap junction protein beta 2 (GJB2) has been associated with glycolysis and immunosuppression in human tumors. This research aims to explore the roles of GJB2 in these aspects in the context of lung adenocarcinoma (LUAD). GJB2 expression in LUAD was analyzed using bioinformatics tools and verified in human LUAD cells. RNA binding proteins (RBPs) that target GJB2 were predicted using bioinformatics and verified using RNA immunoprecipitation assays. Gain- or loss-of-function assays of GJB2 and high-density lipoprotein binding protein (HDLBP) were performed in LUAD cells, investigating their roles in glycolysis. These LUAD cells underwent co-culture with activated CD8⁺ T cells to examine the effect of gene interference on the exhaustion and activity of T cells. A mouse model of allograft tumor was established for in vivo validation. GJB2 exhibited aberrantly heightened expression in LUAD cells. Further overexpression of GJB2 in cancer cells increased glucose uptake, lactate production, and extracellular acidification rate, augmented aggressive phenotype of cancer cells, and increased exhaustion of the co-cultured CD8⁺ T cells. HDLBP, an RBP that binds to GJB2 RNA, was found to be highly expressed in LUAD as well, which enhanced GJB2 expression by stabilizing the GJB2 mRNA. Overexpression of HDLBP similarly rendered glycolysis and T cell inactivity, with these effects negated by GJB2 knockdown. Parallelly, GJB2 silencing in mouse 3LL cells suppressed tumorigenesis, glycolysis, and T cell exhaustion in mice promoted by HDLBP. This research suggests that HDLBP-mediated GJB2 RNA stabilization augments glycolysis and CD8⁺ T cell exhaustion in LUAD progression.