Endoplasmic Reticulum stress-induced calcium release activates PERK pathway

FERNÁNDEZ M., ; VILCHEZ ARUANI J.; DE BATISTA, J.; BOLLO, M.

Congreso; LVII Congreso Anual de la Sociedad Argentina de Bioquímica y Bilogía Celular; 2021

SAIB

ENDOPLASMIC RETICULUMSTRESS-INDUCED CALCIUM INCREASE ACTIVATES PERK PATHWAY.Fernández M1, Vilchez Aruani J1,De Battista J. C2, Bollo M11 Instituto deInvestigación Médica M y M Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina.2 Hospital Privado Universitario de Córdoba,Instituto Universitario de Ciencias Biomédicas de Córdoba (IUCBC),  Córdoba, ArgentinaE-mail: maquifernandez@immf.uncor.edu TheEndoplasmic Reticulum (ER) is a dynamic organelle where are performed numerousfunctions, such as: storage and release of Ca2+, lipid synthesis,folding and post-transductional modifications of proteins. All these processesare interconnected and can be performed only if the Ca2+concentration in the lumen is optimal, this Ca2+ acts as a keymessenger. When the loaded of newly synthesized proteins exceeds the foldingand/or processing capacity in the organelle, the ER enters into stresscondition. To restore the homeostasis, the organelle activates a signalingtransduction pathway collectively termed the Unfolded Protein Response (UPR). (PKR)-like-ER kinase (PERK) is an early stress response ER-transmembraneprotein that is generally inactive due to its association with the chaperoneBiP.DuringER stress, BiP is tritrated by the unfolded protein, leading PERK activationand phosphorylation of eukaryotic initiation factor-2 alpha (eIF2 a), which attenuates proteinsynthesis. We demonstrated that calcineurin-A/B(CN-A/B), an heterotrimeric Ca2+ protein, directly associateswith PERK, increasing its auto-phosphorylation and significantly enhancinginhibition of protein translation. It has also been observed that the βisoform of subunit A of CN (CN-Aβ) in astrocytes has an importantPERK-dependent cytoprotective effect. Althoughthe involvement of Ca2+ signaling in a multitude of cellular functionshas been well documented, little is known about its role inrestoring homeostasis, once UPR is activated. Recently, we described an activeER Ca2+ release through the translocon during acute phase of UPR.The translocon is a protein complex formed by a heterotrimeric core (Sec61α, β,γ). Sec61α, extends on the ER lipid bilayer and forms the channel pore. Here, weevaluated, in astrocytes, the dependence of Ca2+ on PERK activation byimmunocytochemistry as well PERK/CN interaction and eIF2α phosphorylation,after induces stress and pharmacologically modify translocon activity. Moreover,we demonstrated that, using a cell line deficient in all isoforms of IP3receptor and by performing blue native PAGE followed by two-dimensional gel, PERKforms a macromolecular complex with the translocon (Sec61α) and CN, understress condition. 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