Faculté des sciences

Calretinin regulates Ca²⁺-dependent inactivation and facilitation of Cav2.1 Ca²⁺ channels through a direct interaction with the α₁2.1 subunit

Christel, Carl J. ; Schaer, Raphael ; Wang, Shiyi ; Henzi, Thomas ; Kreiner, Lisa ; Grabs, Detlev ; Schwaller, Beat ; Lee, Amy

In: Journal of Biological Chemistry, 2012, p. -

Voltage-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... More

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    Summary
    Voltage-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.