Calcipressin 1 is an endogenous inhibitor of calcineurin, which is a serine/threonine phosphatase under the control of Ca2+ and calmodulin. Calcipressin 1 is encoded by DSCR1, a gene on human chromosome 21 with seven exons, exons 1–4 are alternative first exons (isoforms 1–4). We show that calcipressin 1 isoform 1 has an N-terminal coding region longer than that previously described, and this generates a new polypeptide of 252 amino acids. This polypeptide is able to interact with calcineurin A and to inhibit NF-AT-mediated transcriptional activation. We demonstrate for the first time that endogenous calcipressin 1 exists as a complex together with the calcineurin A and B heterodimer. Calcipressin 1 is a phosphoprotein that increases its capacity to inhibit calcineurin when phosphorylated at the FLISPP motif, and this phosphorylation also controls the half-life of calcipressin 1 by accelerating its degradation. Additionally, we have also detected further phosphorylation sites outside the FLISPP motif and these contribute to the complex phosphorylation pattern of calcipressin 1. Taking all these results into consideration we suggest that phosphorylation of calcipressin 1 is involved in the regulation of the phosphatase activity of calcineurin and can therefore act as a modulator of calcineurin-dependent cellular pathways.
- calcineurin endogenous inhibitor
- FLISPP motif
The nucleotide sequence data reported for the human and murine CALP1L encoding gene (DSCR1) have been submitted to the EMBL, GenBank®, DDBJ and GSDB Nucleotide Sequence Databases under the accession numbers AY325903 and AY325904 respectively.
Abbreviations used: AP, alkaline phosphatase; β-gal, β-galactosidase; CALP, calcipressin; CALP1L, CALP 1-Long; CALP1S, CALP 1-Short; CaM, calmodulin; CnA, calcineurin A; CnB, calcineurin B; 2D-GE, two-dimensional gel electrophoresis; DTT, dithiothreitol; GST, glutathione S-transferase; HA, haemagglutinin; IEF, isoelectric focusing; IAM, iodoacetamide; MEF2, myocyte enhancer factor 2; wt, wild-type; NF-AT, nuclear factor of activated T-cells.
- The Biochemical Society, London ©2003