Calcium sensing by human medullary thyroid carcinoma cells

Ridefelt, Peter; Liu, Yi-Jia; Rastad, Jonas; Åkerström, Göran; Gylfe, Erik

doi:10.1016/0014-5793(94)80200-9

Cited by 8 publications

(1 citation statement)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Downstream intracellular signaling responses, such as the production of IP 1 and the activity of ERK 1/2 , which will be discussed later, can be reflected in the oscillation patterns associated with the different disease-related mutations. Although most research has focused on intracellular calcium mobilization in HEK293 cells heterologously expressing the CaSR, CaSR-induced [Ca 2+ ] i oscillations have also been found in cells with endogenously expressed CaSR, for instance in parathyroid cells [31], bovine anterior pituitary cells [32], opossum kidney (OK) cells [33] and medullary thyroid carcinoma cells [34]. Oscillations in [Ca 2+ ] i modulate not only the rate of parathyroid hormone (PTH) secretion, but also gene expression and other processes [35]–[38].…”

Section: Discussionmentioning

confidence: 99%

Role of Ca2+ and L-Phe in Regulating Functional Cooperativity of Disease-Associated “Toggle” Calcium-Sensing Receptor Mutations

et al. 2014

View full text Add to dashboard Cite

The Ca2+-sensing receptor (CaSR) regulates Ca2+ homeostasis in the body by monitoring extracellular levels of Ca2+ ([Ca2+]o) and amino acids. Mutations at the hinge region of the N-terminal Venus flytrap domain (VFTD) produce either receptor inactivation (L173P, P221Q) or activation (L173F, P221L) related to hypercalcemic or hypocalcemic disorders. In this paper, we report that both L173P and P221Q markedly impair the functional positive cooperativity of the CaSR as reflected by [Ca2+]o–induced [Ca2+]i oscillations, inositol-1-phosphate (IP1) accumulation and extracellular signal-regulated kinases (ERK1/2) activity. In contrast, L173F and P221L show enhanced responsiveness of these three functional readouts to [Ca2+]o. Further analysis of the dynamics of the VFTD mutants using computational simulation studies supports disruption in the correlated motions in the loss-of-function CaSR mutants, while these motions are enhanced in the gain-of-function mutants. Wild type (WT) CaSR was modulated by L-Phe in a heterotropic positive cooperative way, achieving an EC50 similar to those of the two activating mutations. The response of the inactivating P221Q mutant to [Ca2+]o was partially rescued by L-Phe, illustrating the capacity of the L-Phe binding site to enhance the positive homotropic cooperativity of CaSR. L-Phe had no effect on the other inactivating mutant. Moreover, our results carried out both in silico and in intact cells indicate that residue Leu173, which is close to residues that are part of the L-Phe-binding pocket, exhibited impaired heterotropic cooperativity in the presence of L-Phe. Thus, Pro221 and Leu173 are important for the positive homo- and heterotropic cooperative regulation elicited by agonist binding.

show abstract