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Plasma membrane poration by opioid neuropeptides: a possible mechanism of pathological signal transduction.

Maximyuk O, Khmyz V, Lindskog CJ, Vukojević V, Ivanova T, Bazov I, Hauser KF, Bakalkin G, Krishtal O - Cell Death Dis (2015)

Bottom Line: The dynorphins, endogenous ligands for opioid receptors, are an exception; they also produce non-receptor-mediated effects causing pain and neurodegeneration.The potency of dynorphins to porate the plasma membrane correlates with their pathogenic effects in cellular and animal models.Persistent neuronal excitation by this mechanism may lead to profound neuropathological alterations, including neurodegeneration and cell death.

View Article: PubMed Central - PubMed

Affiliation: State Key Lab for Molecular Biology, Bogomoletz Institute of Physiology, Kiev, Ukraine.

ABSTRACT
Neuropeptides induce signal transduction across the plasma membrane by acting through cell-surface receptors. The dynorphins, endogenous ligands for opioid receptors, are an exception; they also produce non-receptor-mediated effects causing pain and neurodegeneration. To understand non-receptor mechanism(s), we examined interactions of dynorphins with plasma membrane. Using fluorescence correlation spectroscopy and patch-clamp electrophysiology, we demonstrate that dynorphins accumulate in the membrane and induce a continuum of transient increases in ionic conductance. This phenomenon is consistent with stochastic formation of giant (~2.7 nm estimated diameter) unstructured non-ion-selective membrane pores. The potency of dynorphins to porate the plasma membrane correlates with their pathogenic effects in cellular and animal models. Membrane poration by dynorphins may represent a mechanism of pathological signal transduction. Persistent neuronal excitation by this mechanism may lead to profound neuropathological alterations, including neurodegeneration and cell death.

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Pore size estimation. (a) Application of 1 μM Big Dyn at holding voltage of −100 mV elicited the appearance of progressively increasing basal current noise of HEK293 cells. (b) Indicated fragments of basal current recording from (a) are shown in milliseconds time scale. (c) All current surges under Big Dyn from the cell shown on (a) were used for estimation of event mode amplitude, resulting mode diameter of pore near 2.7 nm. The holding voltage was −100 mV, NMDG-HEPES solutions (see Materials and Methods) was used in this experiment to minimize errors connected with activities of basal ionic conductances
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fig5: Pore size estimation. (a) Application of 1 μM Big Dyn at holding voltage of −100 mV elicited the appearance of progressively increasing basal current noise of HEK293 cells. (b) Indicated fragments of basal current recording from (a) are shown in milliseconds time scale. (c) All current surges under Big Dyn from the cell shown on (a) were used for estimation of event mode amplitude, resulting mode diameter of pore near 2.7 nm. The holding voltage was −100 mV, NMDG-HEPES solutions (see Materials and Methods) was used in this experiment to minimize errors connected with activities of basal ionic conductances

Mentions: Substitution of small ions for the large ones (HEPES− and NMDG+, NMGD-HEPES solution) does not prevent the appearance of Big Dyn-induced events pointing at the absence of ion specificity of the observed conductance changes (Figures 5a and b). Assuming that these events are associated with pore formation in the membrane, we have roughly estimated the most probable diameter of the pores by measuring mode conductance value (Figure 5). Assuming that the pore is a uniform cylinder of radius r, height h and that intra- and extracellular solutions have resistivity ρ, we can express pore resistance as Rpore = (h+(ρr)/2)ρ/πr2 using the model proposed by Hille.49 As the pore conductance g is the inverse of Rpore and solution conductivity σ is the inverse of resistivity ρ, the above equation for Rpore can be rearranged to determine pore diameter d, from: The mode pore conductance g (16 pA/100 mV=0.16 nS) was estimated from the amplitude histogram (Figure 5c), the conductivity of NMDG-HEPES solutions was ~0.26 S/m and pore height h was estimated as the typical cell plasma membrane thickness of ~7 nm. These estimates resulted in the mode pore diameter of ~2.7 nm.


Plasma membrane poration by opioid neuropeptides: a possible mechanism of pathological signal transduction.

Maximyuk O, Khmyz V, Lindskog CJ, Vukojević V, Ivanova T, Bazov I, Hauser KF, Bakalkin G, Krishtal O - Cell Death Dis (2015)

Pore size estimation. (a) Application of 1 μM Big Dyn at holding voltage of −100 mV elicited the appearance of progressively increasing basal current noise of HEK293 cells. (b) Indicated fragments of basal current recording from (a) are shown in milliseconds time scale. (c) All current surges under Big Dyn from the cell shown on (a) were used for estimation of event mode amplitude, resulting mode diameter of pore near 2.7 nm. The holding voltage was −100 mV, NMDG-HEPES solutions (see Materials and Methods) was used in this experiment to minimize errors connected with activities of basal ionic conductances
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4385918&req=5

fig5: Pore size estimation. (a) Application of 1 μM Big Dyn at holding voltage of −100 mV elicited the appearance of progressively increasing basal current noise of HEK293 cells. (b) Indicated fragments of basal current recording from (a) are shown in milliseconds time scale. (c) All current surges under Big Dyn from the cell shown on (a) were used for estimation of event mode amplitude, resulting mode diameter of pore near 2.7 nm. The holding voltage was −100 mV, NMDG-HEPES solutions (see Materials and Methods) was used in this experiment to minimize errors connected with activities of basal ionic conductances
Mentions: Substitution of small ions for the large ones (HEPES− and NMDG+, NMGD-HEPES solution) does not prevent the appearance of Big Dyn-induced events pointing at the absence of ion specificity of the observed conductance changes (Figures 5a and b). Assuming that these events are associated with pore formation in the membrane, we have roughly estimated the most probable diameter of the pores by measuring mode conductance value (Figure 5). Assuming that the pore is a uniform cylinder of radius r, height h and that intra- and extracellular solutions have resistivity ρ, we can express pore resistance as Rpore = (h+(ρr)/2)ρ/πr2 using the model proposed by Hille.49 As the pore conductance g is the inverse of Rpore and solution conductivity σ is the inverse of resistivity ρ, the above equation for Rpore can be rearranged to determine pore diameter d, from: The mode pore conductance g (16 pA/100 mV=0.16 nS) was estimated from the amplitude histogram (Figure 5c), the conductivity of NMDG-HEPES solutions was ~0.26 S/m and pore height h was estimated as the typical cell plasma membrane thickness of ~7 nm. These estimates resulted in the mode pore diameter of ~2.7 nm.

Bottom Line: The dynorphins, endogenous ligands for opioid receptors, are an exception; they also produce non-receptor-mediated effects causing pain and neurodegeneration.The potency of dynorphins to porate the plasma membrane correlates with their pathogenic effects in cellular and animal models.Persistent neuronal excitation by this mechanism may lead to profound neuropathological alterations, including neurodegeneration and cell death.

View Article: PubMed Central - PubMed

Affiliation: State Key Lab for Molecular Biology, Bogomoletz Institute of Physiology, Kiev, Ukraine.

ABSTRACT
Neuropeptides induce signal transduction across the plasma membrane by acting through cell-surface receptors. The dynorphins, endogenous ligands for opioid receptors, are an exception; they also produce non-receptor-mediated effects causing pain and neurodegeneration. To understand non-receptor mechanism(s), we examined interactions of dynorphins with plasma membrane. Using fluorescence correlation spectroscopy and patch-clamp electrophysiology, we demonstrate that dynorphins accumulate in the membrane and induce a continuum of transient increases in ionic conductance. This phenomenon is consistent with stochastic formation of giant (~2.7 nm estimated diameter) unstructured non-ion-selective membrane pores. The potency of dynorphins to porate the plasma membrane correlates with their pathogenic effects in cellular and animal models. Membrane poration by dynorphins may represent a mechanism of pathological signal transduction. Persistent neuronal excitation by this mechanism may lead to profound neuropathological alterations, including neurodegeneration and cell death.

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