Connexin 43 subcellular localization: From trafficking dynamics to pathophysiological outcomes and therapeutic opportunities.

Connexin 43 (Cx43) exhibits remarkable functional diversity that is precisely dictated by its dynamic subcellular localization. Beyond its canonical role at the plasma membrane, where it assembles into gap junctions (GJs) and hemichannels (HCs) to mediate intercellular communication, Cx43 translocates to the nucleus and mitochondria, where it exerts non-channel functions including transcriptional regulation and metabolic adaptation. At the plasma membrane, dysregulation of Cx43 trafficking, anchoring, or turnover leads to excessive HC opening and impaired GJ communication, contributing to cardiovascular arrhythmias, ischemia-reperfusion injury, neuroinflammation, osteoporosis, and retinopathy. In the nucleus, Cx43 or its C-terminal fragment enters through importin-dependent pathways, functioning as a non-canonical transcriptional regulator; its mislocalization is implicated in cancer (context-dependent suppression or promotion), hepatic gluconeogenesis in diabetes, and tissue fibrosis. Within mitochondria, Cx43 is imported via Hsp90/TOM complex- or GJA1-20 k-dependent pathways, where it regulates K+ transport, respiratory chain activity, and redox balance; this mitochondrial pool exerts cardioprotection under preconditioning but exacerbates diabetic cardiomyopathy and neurological injury under pathological stress. This review synthesizes current knowledge on the trafficking mechanisms, pathological outcomes, and therapeutic targeting of Cx43 in these three subcellular compartments. We further discuss peptide-based inhibitors (e.g., Gap19, αCT1), small molecules (e.g., tonabersat, danegaptide), and natural product-derived modulators, highlighting challenges in specificity, bioavailability, and clinical translation. By linking compartment-specific functions to distinct disease entities, this review establishes subcellular localization as a central determinant of Cx43 biology and a promising axis for precision medicine.