In contrast to other PxIxIT peptides, this motif inhibits the phosphatase action towards the RII phosphopeptide. Overexpression of AKAP79330 357 in HEK293 cells antagonizes the interac tion involving AKAP79 and calcineurin. The endogenous inhibitory protein CABIN1 incorporates a conserved PEITVT motif. A peptide spanning the residues 2078 2115 of rat CABIN1 binds to calcineurin, and human CABIN12143 2220 overexpression in Jurkat T cells inhibits NFATc dephosphorylation and NFAT dependent luciferase expression. Both fragments overlap at the KFPPEITVTPP sequence. For that reason, this motif is assumed to take part in the CABIN1 calcineurin interaction. RCAN1, an endogenous modulator of calcineurin activity, is expressed in sev eral splice variants which vary in their N termini but share an identical C terminus.
On this critique, the amino acid designation continues to be adapted from your splice variant RCAN1 you can find out more four, though many cited publications use the designation from the splice variant 1 one. RCAN1 exon7, containing the C terminus, binds to full length calcineurin and to a catalytic core frag ment of calcineurin too as complete length RCAN1. Each, RCAN1 exon7 and complete length RCAN1, inhibit competi tively the dephosphorylation of pNPP in enzyme assays as well as calcineurin mediated nuclear translocation of NFATc3 within the BHK cell line after their overexpression. At first, the PKIIQT motif within this region was viewed as to mimic the NFATc PxIxIT motif and to inhibit NFATc calcineurin interaction, but a pep tide spanning the residues 178 191 did not compete with VIVIT peptide for binding to calcineurin. Latest experi ments unveiled that the RCAN1 4136 163 fragment is made up of a region named calcineurin inhibitor calcipressin 1 motif, which can be displaced from calcineurin by the VIVIT peptide.
The RCAN1 4143 163 CIC fragment binds kinase inhibitor ONX-0914 to calcineurin A with high affinity, competes with all the bind ing of VIVIT peptide, and inhibits NFATc2 nuclear trans location too as NFATc dependent reporter gene expression in transfected COS 7 cells. Importantly, this fragment doesn’t interfere together with the phosphatase action of calcineurin in the direction of RII phosphopeptide and homolo gous regions are observed from the related proteins RCAN2 and RCAN3. This fragment is made up of the true PxIxIT motif of RCANs PSVVVH, which binds to your similar hydrophobic pocket of calcineurin as the VIVIT peptide. As a result, the PSV VVH peptide competes with all the regula tory region of NFATc2 or GST CABIN1 for binding to calcineurin. A peptide derived through the C terminus of the yeast RCAN homologue Rcn2, containing the PSITVN motif, is in a position to compete using the VIVIT peptide for bind ing to human calcineurin, also. Consequently, deletion of this motif in Rcn2 abolishes its inhibition of calcineurin signalling in yeast.