The receptor-associated protein (RAP) binds calmodulin and is phosphorylated by calmodulin-dependent kinase II

C M Petersen; L Ellgaard; A Nykjaer; F Vilhardt; H Vorum; H C Thøgersen; M S Nielsen; C Jacobsen; S K Moestrup; J Gliemann

The receptor-associated protein (RAP) binds calmodulin and is phosphorylated by calmodulin-dependent kinase II

EMBO J. 1996 Aug 15;15(16):4165-73.

Authors

C M Petersen¹, L Ellgaard, A Nykjaer, F Vilhardt, H Vorum, H C Thøgersen, M S Nielsen, C Jacobsen, S K Moestrup, J Gliemann

Affiliation

¹ Department of Medical Biochemistry, University of Aarhus, Denmark.

PMID: 8861945
PMCID: PMC452140

Abstract

The receptor-associated protein, RAP, is an intracellular protein that may function as a chaperone for the LDL-receptor family receptors. Here we report calmodulin as the first identified RAP binding protein outside of the LDL-receptor family members. We demonstrate that RAP binds calmodulin in a Ca2+- and pH-dependent manner characteristic of calmodulin-dependent enzymes, and present evidence that RAP is a substrate for calmodulin-dependent enzymes. Thus, CaM-kinase II and calcineurin readily phosphorylate and dephosphorylate, respectively, serine residues in RAP, and in the individual RAP domains D2 (amino acids 113-218) and D3 (amino acids 219-323) which both contain sites for CaM-kinase II-mediated phosphorylation and for calmodulin binding. In addition, we provide evidence that RAP is phosphorylated by other kinases such as casein kinase II. Studies of 32[ortho]P-labelled cell cultures demonstrate that RAP is phosphorylated in vivo. Our results suggest that RAP may have hitherto unknown functions implicating phosphorylation and calmodulin-mediated modulation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amino Acid Sequence
Calcineurin
Calcium / metabolism
Calcium-Calmodulin-Dependent Protein Kinase Type 2
Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
Calmodulin / metabolism*
Calmodulin-Binding Proteins / metabolism
Carrier Proteins / metabolism*
Casein Kinase II
Glycoproteins / metabolism*
Hydrogen-Ion Concentration
LDL-Receptor Related Protein-Associated Protein
Molecular Sequence Data
Phosphoprotein Phosphatases / metabolism
Phosphorylation
Phosphoserine / metabolism
Protein Processing, Post-Translational*
Protein Serine-Threonine Kinases / metabolism
Receptors, LDL / metabolism
Recombinant Fusion Proteins / metabolism

Substances

Calmodulin
Calmodulin-Binding Proteins
Carrier Proteins
Glycoproteins
LDL-Receptor Related Protein-Associated Protein
Receptors, LDL
Recombinant Fusion Proteins
Phosphoserine
Casein Kinase II
Protein Serine-Threonine Kinases
Calcium-Calmodulin-Dependent Protein Kinase Type 2
Calcium-Calmodulin-Dependent Protein Kinases
Calcineurin
Phosphoprotein Phosphatases
Calcium