Human calmodulin methyltransferase: expression, activity on calmodulin, and Hsp90 dependence

• Published in: PloS one 2012-12, Vol.7 (12), p.e52425
• Main Authors: Magen, Sophia, Magnani, Roberta, Haziza, Sitvanit, Hershkovitz, Eli, Houtz, Robert, Cambi, Franca, Parvari, Ruti
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Benzoquinones - pharmacology; Biology; Calcium-binding protein; Calmodulin; Calmodulin - metabolism; Calmodulin-lysine N-methyltransferase; Cancer; Cell Line; Cells (Biology); Chromosome Deletion; Chromosomes, Human, Pair 21 - enzymology; Chromosomes, Human, Pair 21 - genetics; Clonal deletion; Comparative analysis; Craniofacial Abnormalities - enzymology; Craniofacial Abnormalities - genetics; Cystinuria - enzymology; Cystinuria - genetics; Cytoplasm; Disorders; DNA methylation; Exons; Geldanamycin; Gene deletion; Gene expression; Golgi apparatus; Green Fluorescent Proteins - metabolism; Health sciences; Heat shock proteins; Horticulture; HSP90 Heat-Shock Proteins - chemistry; HSP90 Heat-Shock Proteins - metabolism; Hsp90 protein; Humans; Intellectual Disability - enzymology; Intellectual Disability - genetics; Kinases; Lactams, Macrocyclic - pharmacology; Localization; Lysine; Medicine; Methylation; Methylation - drug effects; Methyltransferase; Methyltransferases - chemistry; Methyltransferases - genetics; Methyltransferases - metabolism; Mice; Mice, Inbred ICR; Mitochondrial Diseases - enzymology; Mitochondrial Diseases - genetics; Molecular Sequence Data; Muscle Hypotonia - enzymology; Muscle Hypotonia - genetics; N-Methyltransferase; Nuclei; Nuclei (cytology); Patients; Penicillin; Protein Binding - drug effects; Protein Stability - drug effects; Protein Structure, Tertiary; Protein Transport - drug effects; Proteins; Proteolysis - drug effects; Recombinant Fusion Proteins - metabolism; Subcellular Fractions - drug effects; Subcellular Fractions - enzymology; Target recognition; Tissues; Transcription; Transcription, Genetic - drug effects; Transferases; Virology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0052425

Deletion of the first exon of calmodulin-lysine N-methyltransferase (CaM KMT, previously C2orf34) has been reported in two multigene deletion syndromes, but additional studies on the gene have not been reported. Here we show that in the cells from 2p21 deletion patients the loss of CaM KMT expression results in accumulation of hypomethylated calmodulin compared to normal controls, suggesting that CaM KMT is essential for calmodulin methylation and there are no compensatory mechanisms for CaM methylation in humans. We have further studied the expression of this gene at the transcript and protein levels. We have identified 2 additional transcripts in cells of the 2p21 deletion syndrome patients that start from alternative exons positioned outside the deletion region. One of them starts in the 2(nd) known exon, the other in a novel exon. The transcript starting from the novel exon was also identified in a variety of tissues from normal individuals. These new transcripts are not expected to produce proteins. Immunofluorescent localization of tagged CaM KMT in HeLa cells indicates that it is present in both the cytoplasm and nucleus of cells whereas the short isoform is localized to the Golgi apparatus. Using Western blot analysis we show that the CaM KMT protein is broadly expressed in mouse tissues. Finally we demonstrate that the CaM KMT interacts with the middle portion of the Hsp90 molecular chaperon and is probably a client protein since it is degraded upon treatment of cells with the Hsp90 inhibitor geldanamycin. These findings suggest that the CaM KMT is the major, possibly the single, methyltransferase of calmodulin in human cells with a wide tissue distribution and is a novel Hsp90 client protein. Thus our data provides basic information for a gene potentially contributing to the patient phenotype of two contiguous gene deletion syndromes.