Joubert syndrome causing mutation in C2 domain of CC2D2A affects structural integrity of cilia and cellular signaling molecules.

Cilia are organelles extend from cells to sense external signals for tuning intracellular signaling for optimal cellular functioning. They have evolved sensory and motor roles in various cells for tissue organization and homeostasis in development and post-development. More than a thousand genes are required for cilia function. Mutations in them cause multisystem disorders termed ciliopathies. The null mutations in CC2D2A result in Meckel syndrome (MKS), which is embryonic lethal, whereas patients who have missense mutations in the C2 domain of CC2D2A display Joubert syndrome (JBTS). They survive with blindness and mental retardation. How C2 domain defects cause disease conditions is not understood. To answer this question, C2 domain of Cc2d2a (mice gene) was knocked down (KD) in IMCD-3 cells by shRNA. This resulted in defective cilia morphology observed by immunofluorescence analysis. To further probe the cellular signaling alteration in affected cells, gene expression profiling was done by RNAseq and compared with the controls. Bioinformatics analysis revealed that the differentially expressed genes (DEGs) have functions in cilia. Among the 61 cilia DEGs identified, 50 genes were downregulated and 11 genes were upregulated. These cilia genes are involved in cilium assembly, protein trafficking to the cilium, intraflagellar transport (IFT), cellular signaling like polarity patterning, and Hedgehog signaling pathway. This suggests that the C2 domain of CC2D2A plays a critical role in cilia assembly and molecular signaling hosted in cilia for cellular homeostasis. Taken together, the missense mutations in the C2 domain of CC2D2A seen in JBTS might have affected cilia-mediated signaling in neurons of the retina and brain.

Hydrogen Sulfide-Induced Activatable Photodynamic Therapy Adjunct to Disruption of Subcellular Glycolysis in Cancer Cells by a Fluorescence-SERS Bimodal Iridium Metal-Organic Hybrid.

The practical application of photodynamic therapy (PDT) demands targeted and activatable photosensitizers to mitigate off-target phototoxicity common in "always on" photosensitizers during light exposure. Herein, a cyclometalated iridium complex-based activatable photodynamic molecular hybrid, Cy-Ir-7-nitrobenzofurazan (NBD), is demonstrated as a biomedicine for molecular precision. This design integrates a hydrogen sulfide (H2S)-responsive NBD unit with a hydroxy-appended iridium complex, Cy-Ir-OH. In normal physiological conditions, the electron-rich Ir metal center exerts electron transfer to the NBD unit, quenches the excited state dynamics, and establishes a PDT-off state. Upon exposure to H2S, Cy-Ir-NBD activates into the potent photosensitizer Cy-Ir-OH through nucleophilic substitution. This mechanism ensures exceptional specificity, enabling targeted phototherapy in H2S-rich cancer cells. Additionally, we observed that Cy-Ir-NBD-induced H2S depletion disrupts S-sulfhydration of the glyceraldehyde-3-phosphate dehydrogenase enzyme, impairing glycolysis and ATP production in the cellular milieu. This sequential therapeutic process of Cy-Ir-NBD is governed by the positively charged central iridium ion that ensures mitochondria-mediated apoptosis in cancer cells. Dual-modality SERS and fluorescence imaging validate apoptotic events, highlighting Cy-Ir-NBD as an advanced theranostic molecular entity for activatable PDT. Finally, as a proof of concept, clinical assessment is evaluated with the blood samples of breast cancer patients and healthy volunteers, based on their H2S overexpression capability through SERS and fluorescence, revealing Cy-Ir-NBD to be a promising predictor for PDT activation in advanced cancer phototherapy.