Calcium Sensing Receptor

The extracellular calcium sensing and homeostasis mechanism consist of a G-protein coupled receptor linked to gq and Gi and phosphoinositide turnover and inhibition of parathyroid hormone (PTH) secretion.  In cells, the calcium homeostasis is via voltage-dependent L-type calcium channel and calcium sensing receptor  (CaSR).  The CaSR gene is derived from the CaSR gene expressed in parathyroid glands, CaSR is expressed in at least 2 variant isoforms CaSR and CaSRb.  The CaSr senses small changes in the circulating Ca concentrations and couples this information to intracellular signaling pathways that modify .  of CaThe activation of CaSR led to inhibition of PTH secretion and stimulation of calcitonin secretion in human medularyC cells (1).  Defects in the human Ca(2+)-sensing receptor gene have been shown to cause familial hypocalciuric hypercalcaemia and neonatal severe hyperparathyroidism.  Several  mutations in CaSR gene caused a missense mutation (228Arg-->Gln, 39Thr-->Met, 144Gly-->Glu, 63Arg-->Met, and 67Arg-->Cys) that encodes a non-conservative amino acid alteration. These mutations are each predicted to be in the Ca(2+)-sensing receptor’s large extracellular domain (2). CaSR are expressed in kidney cells, where the receptor negatively regulates calcium reabsorption.  Mutation is this gene further augments the hyperclciurea increase and risk of renal complications. A similar Ca sensing receptor has been cloned in osteoblasts (Ob-CaSR) which differs in coupling to serum response factors, the Ob-CaSR activates ternary complex factor (3).  

CaSR is expressed in  kidney, but not in brain, lung, liver, heart, skeletal muscle, or placenta.  The CaSR is member of 7TMD family of GPCRs, that undergoes  N-glycosylation and ubiquitination by RNF19A; which induces proteasomal degradation. The CaSR is a 120kDa protein (1078aa) expressed in the PTH-producing chief cells of the parathyroid gland and in kidneys.  The ability of CaSR to sense cations and amino acids and function like a G-protein coupled receptor suggests that it may belong to the family of receptors characterized by an evolutionarily conserved amino acid sensing motif (ANF) linked to an intra-membranous 7 transmembrane loop region. 

The CaSR-selective antibodies were generated against unique antigenic sequences near N-terminal end (aa 47-69) from the extracytoplasmic loop of the CaSR. The antibodies to CaSR are affinity purified over immobilized antigen based chromatography, and the purified immunoglobulins are stabilized in antibody stabilization buffer. The affinity purified antibodies are also conjugated to FITC and biotin for direct applications in IHC and cell sorting experiments.  FabGennix Int. Inc.,  also provide limited quantities of antigenic blocking peptides for caSR-101AP.  Antibodies to CaSR (CaSR-101AP) will label both  CaSR and CaSRb variants.  Limited quantities of Western blot positive control of rCaSR (PC-CaSR) is also available in ready-to-use buffer for SDS-PAGe and western blotting experiments.       

For research use only, not for diagnostic or therapeutic use.