000030619 001__ 30619 000030619 005__ 20150420164425.0 000030619 0248_ $$aoai:doc.rero.ch:20121115122619-GU$$punifr$$ppostprint$$prero_explore$$particle$$zthesis_urn$$zcdu57$$zreport$$zthesis$$zbook$$zjournal$$zcdu16$$zpreprint$$zcdu1$$zdissertation$$zcdu34 000030619 041__ $$aeng 000030619 080__ $$a57 000030619 100__ $$aChristel, Carl J.$$uuniversity of iowa, United States 000030619 245__ $$9eng$$aCalretinin regulates Ca²⁺-dependent inactivation and facilitation of Ca<sub>v</sub>2.1 Ca²⁺ channels through a direct interaction with the α₁2.1 subunit 000030619 520__ $$9eng$$aVoltage-gated Cav2.1 Ca2+ channels undergo dual modulation by Ca2+, Ca2+-dependent inactivation (CDI) and facilitation (CDF), which can influence synaptic plasticity in the nervous system. While the molecular determinants controlling CDI and CDF have been the focus of intense research, little is known about the factors regulating these processes in neurons. Here, we show that calretinin (CR), a Ca2+ binding protein highly expressed in subpopulations of neurons in the brain, inhibits CDI and enhances CDF by binding directly to α₁2.1. Screening of a phage display library with CR as bait revealed a highly basic CR-binding domain (CRB) present in multiple copies in the cytoplasmic linker between domains II and III of α₁2.1. In pull-down assays, CR binding to fusion proteins containing these CRBs was largely Ca2+-dependent. α12.1 coimmunoprecipitated with CR antibodies from transfected cells and mouse cerebellum, which confirmed the existence of CR-Cav2.1 complexes in vitro and in vivo. In HEK293T cells, CR significantly decreased Cav2.1 CDI and increased CDF. CR binding to α₁2.1 was required for these effects, since they were not observed upon substitution of the II-III linker of α₁2.1 with that from the Cav1.2 α₁ subunit (α₁1.2) which lacks the CRBs. In addition, coexpression of a protein containing the CRBs blocked the modulatory action of CR, most likely by competing with CR for interactions with α₁2.1. Our findings highlight an unexpected role for CR in directly modulating effectors such as Cav2.1, which may have major consequences for Ca2+-signaling and neuronal excitability. 000030619 695__ $$9eng$$aCalcium ; Calcium binding proteins ; Calcium channels ; Ion channels ; Neurotransmitter release ; EF-hand ; 000030619 700__ $$aSchaer, Raphael$$uUniversity of Fribourg, Switzerland 000030619 700__ $$aWang, Shiyi$$uUniversity of Iowa, United States 000030619 700__ $$aHenzi, Thomas$$uUniversity of Fribourg, Switzerland 000030619 700__ $$aKreiner, Lisa$$uEmory University, United States 000030619 700__ $$aGrabs, Detlev$$uUniversity of Fribourg, Switzerland 000030619 700__ $$aSchwaller, Beat$$uUniversity of Fribourg, Switzerland 000030619 700__ $$aLee, Amy$$uUniversity of Iowa, United States 000030619 773__ $$g2012///-$$tJournal of Biological Chemistry 000030619 775__ $$gPublished version$$ohttp://dx.doi.org/10.1074/jbc.M112.406363 000030619 8564_ $$fsch_crc.pdf$$qapplication/pdf$$s459445$$uhttps://doc.rero.ch/record/30619/files/sch_crc.pdf$$yorder:1$$zpdf 000030619 918__ $$aFaculté des sciences$$bDécanat, Ch. du Musée 6A, 1700 Fribourg$$cMédecine 000030619 919__ $$aUniversité de Fribourg$$bFribourg$$ddoc.support@rero.ch 000030619 980__ $$aPOSTPRINT$$bUNIFR$$fART_JOURNAL 000030619 990__ $$a20121115122619-GU