Josephs Tracy Maree, Zhang Frankie, Dinh Le Vi, Keller Andrew N, Conigrave Arthur D, Capuano Ben, Gregory Karen Joan, Leach Katie
Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia.
ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia.
J Mol Endocrinol. 2022 May 9;69(1):243-257. doi: 10.1530/JME-21-0263.
Loss-of-function calcium-sensing receptor (CASR) mutations cause mineral metabolism disorders, familial hypocalciuric hypercalcemia, or neonatal severe hyperparathyroidism and increase the risk of femoral fracture, chronic kidney disease, coronary heart disease, and other diseases. In severe cases, CaSR mutations are lethal. Off-label use of the CaSR-positive allosteric modulator (PAM), cinacalcet, corrects hypercalcemia in some patients with CaSR mutations. However, other patients remain unresponsive to cinacalcet, attesting to the need for novel treatments. Here, we compared the effects of cinacalcet to two other clinically approved synthetic CaSR activators, evocalcet and etelcalcetide, as well as a novel PAM, 1-(2,4-dimethylphenyl)-1-(4,5-dimethylthiazol-2-yl)ethan-1-ol (MIPS-VD-836-108) on clinically relevant CaSR mutations. We assessed the compounds in CaSR-expressing HEK293 cells for correction of mutation-induced impairments in intracellular calcium (Ca2+i) mobilization and cell surface expression. While cinacalcet, MIPS-VD-836-108 and evocalcet rescued the signaling of cell surface-expressed mutants, albeit to varying degrees, etelcalcetide was ineffective. Cinacalcet and evocalcet, but not MIPS-VD-836-108 or etelcalcetide, restored the expression of a R680H mutant. However, no compound rescued expression of I81K and C582R mutants or a receptor missing 77 amino acids in the extracellular domain mimicking deletion of CASRexon 5, which impairs CaSR function. These data suggest specific compounds may be clinically effective in some patients with CaSR mutations, but other patients will remain refractory to treatment with currently available CaSR-targeting activators, highlighting the need for new generation drugs to rescue both the signaling and expression of mutant CaSRs.
功能丧失性钙敏感受体（CASR）突变会导致矿物质代谢紊乱、家族性低钙血症性高钙血症或新生儿重症甲状旁腺功能亢进，并增加股骨骨折、慢性肾病、冠心病及其他疾病的风险。在严重情况下，CaSR突变是致命的。钙敏感受体阳性变构调节剂（PAM）西那卡塞的超说明书使用可纠正一些CaSR突变患者的高钙血症。然而，其他患者对西那卡塞仍无反应，这证明需要新的治疗方法。在此，我们比较了西那卡塞与另外两种临床批准的合成CaSR激活剂依维卡塞和依特卡肽，以及一种新型PAM 1-(2,4-二甲基苯基)-1-(4,5-二甲基噻唑-2-基)乙醇（MIPS-VD-836-108）对临床相关CaSR突变的影响。我们在表达CaSR的HEK293细胞中评估了这些化合物对突变诱导的细胞内钙（Ca2+i）动员和细胞表面表达受损的纠正情况。虽然西那卡塞、MIPS-VD-836-108和依维卡塞均能不同程度地挽救细胞表面表达突变体的信号传导，但依特卡肽无效。西那卡塞和依维卡塞可恢复R680H突变体的表达，但MIPS-VD-836-108或依特卡肽则不能。然而，没有一种化合物能挽救I81K和C582R突变体或细胞外结构域缺失77个氨基酸（模拟CASR外显子5缺失）的受体的表达，这种缺失会损害CaSR功能。这些数据表明，特定化合物可能对一些CaSR突变患者具有临床疗效，但其他患者对目前可用的靶向CaSR的激活剂治疗仍将无效，这凸显了需要新一代药物来挽救突变CaSR的信号传导和表达。
