Calpain-5 expression in the retina localizes to photoreceptor synapses

Kellie A. Schaefer, Marcus A. Toral, Gabriel Velez, Allison J. Cox, Sheila A. Baker, Nicholas C. Borcherding, Diana F. Colgan, Vimala Bondada, Charles B. Mashburn, Chen Guang Yu, James W. Geddes, Stephen H. Tsang, Alexander G. Bassuk, Vinit B. Mahajan

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


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 RNAsequencing 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.

Original languageEnglish
Pages (from-to)2509-2521
Number of pages13
JournalInvestigative Ophthalmology and Visual Science
Issue number6
StatePublished - May 2016

Bibliographical note

Funding Information:
Bryan Phillips provided C. elegans protein extracts. Modestos Modestous provided fractionated retina. Melinda Smits, Tyler Mouw, and Nnamdi Nelson provided technical assistance. VBM is Supported by National Institutes of Health (NIH) Grants K08EY020530, R01EY024665, R01EY025225, R01EY024698, and R21AG050437 (VBM); Doris Duke Charitable Foundation Grant #2013103 and Research to Prevent Blindness (RPB; New York, NY, USA); and by NIH Grant T32GM007337 (MT, GV, NCB).

Publisher Copyright:
© 2016, Association for Research in Vision and Ophthalmology Inc. All rights reserved.


  • Autosomal dominant neovascular inflammatory vitreoretinopathy
  • CAPN5
  • Calpain

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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