EF-hand proteins are ubiquitous in cell signaling. Parvalbumin (Parv), the archetypal EF-hand protein, is a high-affinity Ca2+ buffer in many biological systems. Given the centrality of Ca2+ signaling in health and disease, EF-hand motifs designed to have new biological activities may have widespread utility. Here, an EF-hand motif substitution that had been presumed to destroy EF-hand function, that of glutamine for glutamate at position 12 of the second cation binding loop domain of Parv (ParvE101Q), markedly inverted relative cation affinities: Mg2+ affinity increased, whereas Ca 2+ affinity decreased, forming a new ultra-delayed Ca2+ buffer with favorable properties for promoting cardiac relaxation. In therapeutic testing, expression of ParvE101Q fully reversed the severe myocyte intrinsic contractile defect inherent to expression of native Parv and corrected abnormal myocardial relaxation in diastolic dysfunction disease models in vitro and in vivo. Strategic design of new EF-hand motif domains to modulate intracellular Ca2+ signaling could benefit many biological systems with abnormal Ca2+ handling, including the diseased heart.
Bibliographical noteFunding Information:
We thank T. Herron, E. Devaney, I. Turner, M. Maerz, F. Sjaastad, B. Liu, S. Little and T. Edwards for their assistance. We thank the Lillehei Heart Institute for support. We thank H. Sabbah (Henry Ford Hospital Heart and Vascular Institute) for providing the canine failing myocytes. We thank K.B. Andersson and G. Christensen (Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Norway) for providing the mice with inducible cardiac myocyte–specific excision of the SERCA2a. This work was supported by the US National Institutes of Health (J.M.M. and J.D.P.).
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