Liaison between Myristoylation and Cryptic EF-Hand
Motif Confers Ca<sup>2+</sup> Sensitivity to Neuronal Calcium Sensor‑1
- Publication date
- 2015
- Publisher
Abstract
Many members of the neuronal calcium
sensor (NCS) protein family
have a striking coexistence of two characteristics, that is, N-myristoylation
and the cryptic EF-1 motif. We investigated the rationale behind this
correlation in neuronal calcium sensor-1 (NCS-1) by restoring Ca<sup>2+</sup> binding ability of the disabled EF-1 loop by appropriate
mutations. The concurrence of canonical EF-1 and N-myristoylation
considerably decreased the overall Ca<sup>2+</sup> affinity, conformational
flexibility, and functional activation of downstream effecter molecules
(i.e., PI4Kβ). Of a particular note, Ca<sup>2+</sup> induced
conformational change (which is the first premise for a CaBP to be
considered as sensor) is considerably reduced in myristoylated proteins
in which Ca<sup>2+</sup>-binding to EF-1 is restored. Moreover, Ca<sup>2+</sup>, which otherwise augments the enzymatic activity of PI4Kβ
(modulated by NCS-1), leads to a further decline in the modulated
PI4Kβ activity by myristoylated mutants (with canonical EF-1)
pointing toward a loss of Ca<sup>2+</sup> signaling and specificity
at the structural as well as functional levels. This study establishes
the presence of the strong liaison between myristoylation and cryptic
EF-1 in NCS-1. Breaking this liaison results in the failure of Ca<sup>2+</sup> specific signal transduction to downstream effecter molecules
despite Ca<sup>2+</sup> binding. Thus, the EF-1 disability is a prerequisite
in order to append myristoylation signaling while preserving structural
robustness and Ca<sup>2+</sup> sensitivity/specificity in NCS-1