@article {2019, title = {Calpains as mechanistic drivers and therapeutic targets for ocular disease.}, journal = {Trends Mol Med}, volume = {28}, year = {2022}, month = {2022 08}, pages = {644-661}, abstract = {

Ophthalmic neurodegenerative diseases encompass a wide array of molecular pathologies unified by calpain dysregulation. Calpains are calcium-dependent proteases that perpetuate cellular death and inflammation when hyperactivated. Calpain inhibition trials in other organs have faced pharmacological challenges, but the eye offers many advantages for the development and testing of targeted molecular therapeutics, including small molecules, peptides, engineered proteins, drug implants, and gene-based therapies. This review highlights structural mechanisms underlying calpain activation, distinct cellular expression patterns, and in vivo models that link calpain hyperactivity to human retinal and developmental disease. Optimizing therapeutic approaches for calpain-mediated eye diseases can help accelerate clinically feasible strategies for treating calpain dysregulation in other diseased tissues.

}, keywords = {Calcium, Calpain, Cell Death, Humans, Retina}, issn = {1471-499X}, doi = {10.1016/j.molmed.2022.05.007}, author = {Vu, Jennifer T and Wang, Elena and Wu, Jolan and Sun, Young Joo and Velez, Gabriel and Bassuk, Alexander G and Lee, Soo Hyeon and Mahajan, Vinit B} } @article {663, title = {Calpain-5 Expression in the Retina Localizes to Photoreceptor Synapses.}, journal = {Invest Ophthalmol Vis Sci}, volume = {57}, year = {2016}, month = {2016 05 01}, pages = {2509-21}, abstract = {

PURPOSE: We characterize calpain-5 (CAPN5) expression in retinal and neuronal subcellular compartments.

METHODS: CAPN5 gene variants were classified using the exome variant server, and RNA-sequencing was used to compare expression of CAPN5 mRNA in the mouse and human retina and in retinoblastoma cells. Expression of CAPN5 protein was ascertained in humans and mice in silico, in mouse retina by immunohistochemistry, and in neuronal cancer cell lines and fractionated central nervous system tissue extracts by Western analysis with eight antibodies targeting different CAPN5 regions.

RESULTS: Most CAPN5 genetic variation occurs outside its protease core; and searches of cancer and epilepsy/autism genetic databases found no variants similar to hyperactivating retinal disease alleles. The mouse retina expressed one transcript for CAPN5 plus those of nine other calpains, similar to the human retina. In Y79 retinoblastoma cells, the level of CAPN5 transcript was very low. Immunohistochemistry detected CAPN5 expression in the inner and outer nuclear layers and at synapses in the outer plexiform layer. Western analysis of fractionated retinal extracts confirmed CAPN5 synapse localization. Western blots of fractionated brain neuronal extracts revealed distinct subcellular patterns and the potential presence of autoproteolytic CAPN5 domains.

CONCLUSIONS: CAPN5 is moderately expressed in the retina and, despite higher expression in other tissues, hyperactive disease mutants of CAPN5 only manifest as eye disease. At the cellular level, CAPN5 is expressed in several different functional compartments. CAPN5 localization at the photoreceptor synapse and with mitochondria explains the neural circuitry phenotype in human CAPN5 disease alleles.

}, keywords = {Animals, Blotting, Western, Calpain, Cattle, Female, Gene Expression Regulation, Neoplastic, Humans, Immunohistochemistry, Male, Mice, Neoplasms, Experimental, Photoreceptor Cells, Retina, Retinal Neoplasms, Retinoblastoma, RNA, Neoplasm, Synapses, Tumor Cells, Cultured}, issn = {1552-5783}, doi = {10.1167/iovs.15-18680}, author = {Schaefer, Kellie A and Toral, Marcus A and Velez, Gabriel and Cox, Allison J and Baker, Sheila A and Borcherding, Nicholas C and Colgan, Diana F and Bondada, Vimala and Mashburn, Charles B and Yu, Chen-Guang and Geddes, James W and Tsang, Stephen H and Bassuk, Alexander G and Mahajan, Vinit B} } @article {699, title = {Structural modeling of a novel CAPN5 mutation that causes uveitis and neovascular retinal detachment.}, journal = {PLoS One}, volume = {10}, year = {2015}, month = {2015}, pages = {e0122352}, abstract = {

CAPN5 mutations have been linked to autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV), a blinding autoimmune eye disease. Here, we link a new CAPN5 mutation to ADNIV and model the three-dimensional structure of the resulting mutant protein. In our study, a kindred with inflammatory vitreoretinopathy was evaluated by clinical eye examinations, DNA sequencing, and protein structural modeling to investigate the disease-causing mutation. Two daughters of an affected mother demonstrated symptoms of stage III ADNIV, with posterior uveitis, cystoid macular edema, intraocular fibrosis, retinal neovascularization, retinal degeneration, and cataract. The women also harbored a novel guanine to thymine (c.750G\>T, p.Lys250Asn) missense mutation in exon 6 of CAPN5, a gene that encodes a calcium-activated cysteine protease, calpain-5. Modeling based on the structures of all known calpains revealed the mutation falls within a calcium-sensitive flexible gating loop that controls access to the catalytic groove. Three-dimensional modeling placed the new mutation in a region adjacent to two previously identified disease-causing mutations, all three of which likely disrupt hydrogen bonding within the gating loop, yielding a CAPN5 with altered enzymatic activity. This is the third case of a CAPN5 mutation leading to inherited uveitis and neovascular vitreoretinopathy, suggesting patients with ADNIV features should be tested for CAPN5 mutations. Structural modeling of novel variants can be used to support mechanistic consequences of the disease-causing variants.

}, keywords = {Base Sequence, Calpain, Computational Biology, DNA Primers, Female, Fluorescein Angiography, Humans, Models, Molecular, Molecular Sequence Data, Mutation, Missense, Pedigree, Phenotype, Protein Conformation, Retinal Detachment, Sequence Analysis, DNA, Tomography, Optical Coherence, Uveitis, Vitreoretinopathy, Proliferative}, issn = {1932-6203}, doi = {10.1371/journal.pone.0122352}, author = {Bassuk, Alexander G and Yeh, Steven and Wu, Shu and Martin, Daniel F and Tsang, Stephen H and Gakhar, Lokesh and Mahajan, Vinit B} } @article {115, title = {Calpain-5 mutations cause autoimmune uveitis, retinal neovascularization, and photoreceptor degeneration.}, journal = {PLoS Genet}, volume = {8}, year = {2012}, month = {2012}, pages = {e1003001}, abstract = {

Autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV) is an autoimmune condition of the eye that sequentially mimics uveitis, retinitis pigmentosa, and proliferative diabetic retinopathy as it progresses to complete blindness. We identified two different missense mutations in the CAPN5 gene in three ADNIV kindreds. CAPN5 encodes calpain-5, a calcium-activated cysteine protease that is expressed in retinal photoreceptor cells. Both mutations cause mislocalization from the cell membrane to the cytosol, and structural modeling reveals that both mutations lie within a calcium-sensitive domain near the active site. CAPN5 is only the second member of the large calpain gene family to cause a human Mendelian disorder, and this is the first report of a specific molecular cause for autoimmune eye disease. Further investigation of these mutations is likely to provide insight into the pathophysiologic mechanisms of common diseases ranging from autoimmune disorders to diabetic retinopathy.

}, keywords = {Amino Acid Sequence, Base Sequence, Calpain, Cell Line, Cells, Cultured, Choroid Diseases, Exome, Exons, Eye Diseases, Hereditary, Female, Gene Expression, Genetic Linkage, Humans, Male, Models, Molecular, Molecular Sequence Data, Mutation, Pedigree, Phenotype, Photoreceptor Cells, Vertebrate, Protein Conformation, Protein Transport, Retinal Degeneration, Sequence Alignment}, author = {Mahajan, Vinit B and Skeie, Jessica M and Bassuk, Alexander G and Fingert, John H and Braun, Terry A and Daggett, Heather T and Folk, James C and Sheffield, Val C and Stone, Edwin M} }