Nuclear-localized Calcineurin Homologous Protein CHP1 Interacts with Upstream Binding Factor and Inhibits Ribosomal RNA Synthesis
Department of Cell and Tissue Biology, University of California, San Francisco, California 94143, USA. Journal of Biological Chemistry
(Impact Factor: 4.57).
11/2010; 285(47):36260-6. DOI: 10.1074/jbc.M110.165555
Calcineurin homologous protein 1 (CHP1) is a widely expressed, 22-kDa myristoylated EF-hand Ca(2+)-binding protein that shares a high degree of similarity with the regulatory B subunit of calcineurin (65%) and with calmodulin (59%). CHP1 localizes to the plasma membrane, the Golgi apparatus, and the nucleus and functions to regulate trafficking of early secretory vesicles, activation of T cells, and expression and transport of the Na-H exchanger NHE1. Although CHP1 contains nuclear export signals, whether its nuclear and cytoplasmic localization is regulated and has distinct functions remain unknown. We show that CHP1 is predominantly in the nucleus in quiescent fibroblasts, is translocated to cytoplasmic compartments with growth medium, and that translocation is inhibited by mutations in the nuclear export motifs. In a screen for proteins co-precipitating with CHP1 in quiescent cells we identified the upstream binding factor UBF, a DNA-binding protein and component of the RNA polymerase I complex regulating RNA synthesis. The CHP1-UBF interaction is restricted to the nucleus and inhibited by Ca(2+). Nuclear retention of CHP1 attenuates the abundance of UBF in the nucleolus and inhibits RNA synthesis when quiescent cells are transferred to growth medium. These data show UBF as a newly identified CHP1-binding protein and regulation of RNA synthesis as a newly identified function for nuclear-localized CHP1, which is distinct from CHP1 functions in the cytosol.
Available from: PubMed Central
- "Calcium binding protein p22 (Chp), which belongs to the EF-hand superfamily of Ca(2+) binding proteins, may act by transducing cellular Ca(2+) signals to downstream effectors in many cell types . It is also known to be an endogenous inhibitor of calcineurin activity  and thus inactivates the T cells of the immune system. Prehypertension showed the symptoms of dizziness, headache, anxiety, and irritability . "
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ABSTRACT: Objective. Hypertension is one of the most common cardiovascular disorders with high mortality. Here we explored the antihypertension effects of Huanglian Jiedu Decoction (HJD) on thoracic aorta gene expression in spontaneous hypertensive rats. Methods. A rat model of spontaneous hypertension was used. The gene change profile of thoracic aorta after JHD treatment was assessed by GeneChip(GC) analysis using the Agilent Whole Rat Genome Oligo Microarray. Results. Hypertension induced 441 genes upregulated and 417 genes downregulated compared with the normal control group. Treatment of HJD resulted in 76 genes downregulated and 20 genes upregulated. GC data analysis showed that the majority of change genes were involved in immune system process, developmental process, and cell death. Conclusion. Hypertension altered expression of many genes that regulate various biological functions. HJD significantly reduced hypertension and altered the gene expression profiles of SHR rats. These changing genes were involved in many cellular functions such as regulating smooth muscle contraction, Ca(2+) homeostasis, and NO pathway. This study provides the potential novel insights into hypertension and antihypertension effects of HJD.
Available from: ncbi.nlm.nih.gov
- "Although it is well established that the dephosphorylation of Crz1p by calcineurin leads to its nuclear translocation (Stathopoulos-Gerontides et al., 1999), there are no reports of the nuclear localization of calcineurin B in the yeasts or filamentous fungi. Nuclear localization of a calcineurin B homologous protein (CHP1) has been reported (Nagita et al., 2003, Jiménez-Vidal et al., 2010). We could not identify any potential NLS sequence in the A. fumigatus CnaB and it is possible that CnaB may translocate into the nucleus with CnaA and CrzA. "
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ABSTRACT: Calcineurin, a heterodimer composed of the catalytic (CnaA) and regulatory (CnaB) subunits, plays key roles in growth, virulence and stress responses of fungi. To investigate the contribution of CnaA and CnaB to hyphal growth and septation, ΔcnaB and ΔcnaAΔcnaB strains of Aspergillus fumigatus were constructed. CnaA colocalizes to the contractile actin ring early during septation and remains at the centre of the mature septum. While CnaB's septal localization is CnaA-dependent, CnaA's septal localization is CnaB-independent, but CnaB is required for CnaA's function at the septum. Catalytic null mutations in CnaA caused stunted growth despite septal localization of the calcineurin complex, indicating the requirement of calcineurin activity at the septum. Compared to the ΔcnaA and ΔcnaB strains, the ΔcnaAΔcnaB strain displayed more defective growth and aberrant septation. While three Ca(2+) -binding motifs in CnaB were sufficient for its association with CnaA at the septum, the amino-terminal arginine-rich domains (16-RRRR-19 and 44-RLRKR-48) are dispensable for septal localization, yet required for complete functionality. Mutation of the 51-KLDK-54 motif in CnaB causes its mislocalization from the septum to the nucleus, suggesting it is a nuclear export signal sequence. These findings confirm a cooperative role for the calcineurin complex in regulating hyphal growth and septation.
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ABSTRACT: Caenorhabditis elegans defecation is a rhythmic behavior, composed of three sequential muscle contractions, with a 50-s periodicity. The motor program is driven by oscillatory calcium signaling in the intestine. Proton fluxes, which require sodium-proton exchangers at the apical and basolateral intestinal membranes, parallel the intestinal calcium flux. These proton shifts are critical for defecation-associated muscle contraction, nutrient uptake, and longevity. How sodium-proton exchangers are activated in time with intestinal calcium oscillation is not known. The posterior body defecation contraction mutant (pbo-1) encodes a calcium-binding protein with homology to calcineurin homologous proteins, which are putative cofactors for mammalian sodium-proton exchangers. Loss of pbo-1 function results in a weakened defecation muscle contraction and a caloric restriction phenotype. Both of these phenotypes also arise from dysfunctions in pH regulation due to mutations in intestinal sodium-proton exchangers. Dynamic, in vivo imaging of intestinal proton flux in pbo-1 mutants using genetically encoded pH biosensors demonstrates that proton movements associated with these sodium-proton exchangers are significantly reduced. The basolateral acidification that signals the first defecation motor contraction is scant in the mutant compared with a normal animal. Luminal and cytoplasmic pH shifts are much reduced in the absence of PBO-1 compared with control animals. We conclude that pbo-1 is required for normal sodium-proton exchanger activity and may couple calcium and proton signaling events.
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