A-Kinase Anchoring Protein 12 is activated in Müller cells in response to stress.

Abstract

Purpose : A-Kinase Anchoring Protein 12 (AKAP12) binds to the regulatory subunit of protein kinase A and serves as a scaffold protein in signal transduction. In the retina, it is an angiogenesis suppressor gene and regulates the formation of the human blood-retinal barrier. We identified that AKAP12 was expressed more in the periphery-dominant Müller cells in response to stress than in the macula-dominant Müller cells. Here, we further explored the expression pattern and function of AKAP12 in the normal and diseased retina.

Methods : We co-stained the AKAP12 protein with the Müller cell-specific marker, CRALBP, in the normal human retina and the retina with diabetic retinopathy (DR) by immunofluorescent staining. The changes of AKAP12 expression in Müller cells in response to retinal stress were further explored in a JR5558 mouse model of retinal diseases. We used siRNA to knock down the AKAP12 in human primary Müller cells in vitro and evaluate their response to photic stress. The viability of huPMCs with or without knockdown under photic stress was assessed by an AlamarBlue viability assay and lactate dehydrogenase cell toxicity assay.

Results : AKAP12 staining was co-localised with the staining of CRALBP. Müller cells mainly expressed AKAP12 in the retinal nerve fibre layer, outer plexiform layer and outer limiting membrane. AKAP12 was patchily upregulated in the retinal nerve fibre layer, inner plexiform and nuclear layers and outer plexiform layer in the macula of the retina with DR. It was also upregulated in the wall of retinal cysts in the retina with DR. The expression of AKAP12 was also activated in the JR5558 mouse diseased retina compared with the C57BL/6J control mouse. We found that the protein level of AKAP12 significantly reduced in the human primary Müller cells after siRNA treatments. We also found that the viability of Müller cells after the siRNAs treatment under light stress decreased by ~20% compared with the cells exposed to dim light as controls. No significant cell death was detected after siRNAs treatment under stress.

Conclusions : The expression of AKAP12 was altered in stressed or diseased Müller cells, suggesting that it could play a vital role in the cellular stress response. This observation may contribute to understanding the unique role of Müller cells in developing retinal degeneration.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.