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Functional specialization of calreticulin domains

Nakamura, K.
Zuppini, A.
Lynch, J.
Ahsan, I.
Krause, R.
Papp, S.
De Smedt, H.
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Published in The Journal of cell biology. 2001, vol. 154, no. 5, p. 961-972
Abstract Calreticulin is a Ca2+-binding chaperone in the endoplasmic reticulum (ER), and calreticulin gene knockout is embryonic lethal. Here, we used calreticulin-deficient mouse embryonic fibroblasts to examine the function of calreticulin as a regulator of Ca2+ homeostasis. In cells without calreticulin, the ER has a lower capacity for Ca2+ storage, although the free ER luminal Ca2+ concentration is unchanged. Calreticulin-deficient cells show inhibited Ca2+ release in response to bradykinin, yet they release Ca2+ upon direct activation with the inositol 1,4,5-trisphosphate (InsP3). These cells fail to produce a measurable level of InsP3 upon stimulation with bradykinin, likely because the binding of bradykinin to its cell surface receptor is impaired. Bradykinin binding and bradykinin-induced Ca2+ release are both restored by expression of full-length calreticulin and the N + P domain of the protein. Expression of the P + C domain of calreticulin does not affect bradykinin-induced Ca2+ release but restores the ER Ca2+ storage capacity. Our results indicate that calreticulin may play a role in folding of the bradykinin receptor, which affects its ability to initiate InsP3-dependent Ca2+ release in calreticulin-deficient cells. We concluded that the C domain of calreticulin plays a role in Ca2+ storage and that the N domain may participate in its chaperone functions.
Keywords AnimalsBradykinin/pharmacologyCalcium/ metabolismCalcium Channels/genetics/metabolismCalcium-Binding Proteins/genetics/ metabolismCalcium-Transporting ATPases/metabolismCalreticulinCell LineEndoplasmic Reticulum/ metabolismEnzyme Inhibitors/pharmacologyFibroblasts/drug effects/physiologyFlow CytometryHomeostasisImmunoblottingInositol 1,4,5-Trisphosphate ReceptorsMiceMice, KnockoutMicroscopy, FluorescenceMolecular Chaperones/genetics/metabolismProtein Isoforms/genetics/metabolismProtein Structure, TertiaryReceptors, Bradykinin/metabolismReceptors, Cytoplasmic and Nuclear/genetics/metabolismRibonucleoproteins/genetics/ metabolismSarcoplasmic Reticulum Calcium-Transporting ATPasesThapsigargin/pharmacologyTransfection
PMID: 11524434
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NAKAMURA, K. et al. Functional specialization of calreticulin domains. In: The Journal of cell biology, 2001, vol. 154, n° 5, p. 961-972. doi: 10.1083/jcb.200102073 https://archive-ouverte.unige.ch/unige:7440

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Deposited on : 2010-06-21

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