Crosstalk of protein clearance, inflammasome, and Ca2+ channels in retinal pigment epithelium derived from age-related macular degeneration patients

Abstract

Degeneration and/or dysfunction of retinal pigment epithelium (RPE) is generally detected as the formation of intracellular and extracellular protein aggregates, called lipofuscin and drusen, respectively, in patients with age-related macular degeneration (AMD), the leading cause of blindness in the elderly population. These clinical hallmarks are linked to dysfunctional protein homeostasis and inflammation and furthermore, are both regulated by changes in intracellular Ca²⁺ concentration. While many other cellular mechanisms have been considered in the investigations of AMD-RPE, there has been relatively little work on understanding the interactions of protein clearance, inflammation, and Ca²⁺ dynamics in disease pathogenesis. Here we established induced pluripotent stem cell-derived RPE from two patients with advanced AMD and from an age- and gender-matched control subject. We studied autophagy and inflammasome activation under disturbed proteostasis in these cell lines and investigated changes in their intracellular Ca²⁺ concentration and L-type voltage-gated Ca²⁺ channels. Our work demonstrated dysregulated autophagy and inflammasome activation in AMD-RPE accompanied by reduced intracellular free Ca²⁺ levels. Interestingly, we found currents through L-type voltage-gated Ca²⁺ channels to be diminished and showed these channels to be significantly localized to intracellular compartments in AMD-RPE. Taken together, the alterations in Ca²⁺ dynamics in AMD-RPE together with dysregulated autophagy and inflammasome activation indicate an important role for Ca²⁺ signaling in AMD pathogenesis, providing new avenues for the development of therapeutic approaches.

Keywords: Heat shock protein (HSP); L-type Ca(2+) channels; age-related macular degeneration; autophagy; calcium; induced pluripotent stem cell (iPS cell) (iPSC); inflammasome; retinal pigment epithelium.