Integrating biological regulatory network analysis and structural bioinformatics to probe CABP4 transcriptional regulation in night blindness

The focus of this study is to exploit the role of calcium-binding protein 4 (CABP4) and calcium Ca²⁺ levels in the regulation of the Cav1.4 channel in rod photoreceptors. Moreover, It also examines the changes in the regulation that contribute to the development of night blindness. A biological regulatory network (BRN) model was developed, to simulate CABP4 regulation under varying Ca²⁺ levels as in normal and disease conditions. Subsequently, the IQ domain of the wild-type and mutant CABP4 was analyzed through molecular docking to exploit the Cav1.4 regulation mechanism. Resultantly, MD simulations were performed to evaluate complex stability, residue fluctuations, and hydrogen bonding interactions. According to the BRN simulation, there was a dynamic response in CABP4 expression due to the variations in Ca²⁺. CABP4, Ca²⁺ modulators serve as a potent therapeutic target. Subsequently, for the identification of the most favorable binding hypothesis molecular docking and simulation studies were conducted. Both wild-type and mutant CABP4 were docked with the IQ domain. The stability of the docked complexes was assessed using MD simulations. The wild CABP4-IQ complex exhibited consistent stability (RMSD ranging from 0.4 to 0.5 nm compared to fluctuations observed in the mutant CABP4-IQ complex (RMSD ranging from 0.2 to 0.8 nm). The residues critical for the interaction between the IQ domain and CABP4 and essential for functional rod photoreceptors were analyzed. This study elucidates the role of CABP4 and Ca²⁺ in night blindness, potentially paving the way for therapeutic interventions targeting these elements.