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Overexpression of tau downregulated the mRNA levels of Kv channels and improved proliferation in N2A cells.

Li X, Hu X, Li X, Hao X - PLoS ONE (2015)

Bottom Line: Furthermore, the macroscopic currents through Kv channels were reduced by 36.5% at +60 mV in tau-transfected N2A cells.Following the cotransfection with tau in HEK293 cells, the mRNA levels and corresponding currents of Kv2.1 were significantly declined compared with single Kv2.1 transfection.Our data indicated that overexpression of tau declined the mRNA levels of Kv channels and related currents.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, China.

ABSTRACT
Microtubule binding protein tau has a crucial function in promoting the assembly and stabilization of microtubule. Besides tuning the action potentials, voltage-gated K+ channels (Kv) are important for cell proliferation and appear to play a role in the development of cancer. However, little is known about the possible interaction of tau with Kv channels in various tissues. In the present study, tau plasmids were transiently transfected into mouse neuroblastoma N2A cells to explore the possible linkages between tau and Kv channels. This treatment led to a downregulation of mRNA levels of several Kv channels, including Kv2.1, Kv3.1, Kv4.1, Kv9.2, and KCNH4, but no significant alteration was observed for Kv5.1 and KCNQ4. Furthermore, the macroscopic currents through Kv channels were reduced by 36.5% at +60 mV in tau-transfected N2A cells. The proliferation rates of N2A cells were also improved by the induction of tau expression and the incubation of TEA (tetraethylammonium) for 48 h by 120.9% and 149.3%, respectively. Following the cotransfection with tau in HEK293 cells, the mRNA levels and corresponding currents of Kv2.1 were significantly declined compared with single Kv2.1 transfection. Our data indicated that overexpression of tau declined the mRNA levels of Kv channels and related currents. The effects of tau overexpression on Kv channels provided an alternative explanation for low sensitivity to anti-cancer chemicals in some specific cancer tissues.

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Overexpression of tau inhibited whole-cell currents through Kv channels.(A) The outward Kv currents were evoked by stepped up to +60 mV for 500 ms at a holding potential of -80 mV in N2A cells. (B) These Kv currents were substantially decreased after tau transfection for 48 h. (C) Current–voltage (I-V) relations of outward Kv currents in the control (white circle) and transfection with tau (black circle). (D) The graph showed that statistic analysis of effects of tau overexpression on whole-cell Kv currents (n = 8). *P<0.05 compared with control. (E) Representative current traces in the absence and presence of tau overexpression. (F) The statistic analysis of effects of tau overexpression the decay time constant at +60 mV (n = 9). *P>0.05 compared with control.
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pone.0116628.g004: Overexpression of tau inhibited whole-cell currents through Kv channels.(A) The outward Kv currents were evoked by stepped up to +60 mV for 500 ms at a holding potential of -80 mV in N2A cells. (B) These Kv currents were substantially decreased after tau transfection for 48 h. (C) Current–voltage (I-V) relations of outward Kv currents in the control (white circle) and transfection with tau (black circle). (D) The graph showed that statistic analysis of effects of tau overexpression on whole-cell Kv currents (n = 8). *P<0.05 compared with control. (E) Representative current traces in the absence and presence of tau overexpression. (F) The statistic analysis of effects of tau overexpression the decay time constant at +60 mV (n = 9). *P>0.05 compared with control.

Mentions: As a concomitant of decreased expression of Kv channels, the macroscopic currents through these channels should be declined after tau transfection. At a holding potential of -80 mV, the outward Kv currents in N2A cells were evoked by depolarization to testing potentials ranging from -80 mV to +60 mV (Fig. 4A). After transfection of N2A cells with tau for 48 h, the outward Kv currents appeared to be significantly declined at different testing potentials (Fig. 4B). In addition, the current–voltage curves (I–V), which were constructed by the data of current amplitudes measured at the various testing pulses, clearly showed the inhibitory effects of tau transfection on outward Kv currents (Fig. 4C). At +60 mV, overexpression of tau reduced currents from 564.3 ± 47.5 pA to 383.1 ± 55.8 pA (Fig. 4D). However, this treatment did not affect inward currents, even at -80 mV. To examine the effects of tau overexpression on the decay rate of outward Kv currents, whole-cell currents elicited during 5 s depolarizing voltage step to +60 mV from the holding potential of -80 mV were well fitted with a single exponential function. In the absence and presence of tau overexpression, the decay time constant τ at +60 mV were 2360.1 ± 131.3 ms and 2405.3 ± 192.6 ms, respectively (Fig. 4E, F). These results showed that tau induction unaffected the decay process of Kv currents (Fig. 4F).


Overexpression of tau downregulated the mRNA levels of Kv channels and improved proliferation in N2A cells.

Li X, Hu X, Li X, Hao X - PLoS ONE (2015)

Overexpression of tau inhibited whole-cell currents through Kv channels.(A) The outward Kv currents were evoked by stepped up to +60 mV for 500 ms at a holding potential of -80 mV in N2A cells. (B) These Kv currents were substantially decreased after tau transfection for 48 h. (C) Current–voltage (I-V) relations of outward Kv currents in the control (white circle) and transfection with tau (black circle). (D) The graph showed that statistic analysis of effects of tau overexpression on whole-cell Kv currents (n = 8). *P<0.05 compared with control. (E) Representative current traces in the absence and presence of tau overexpression. (F) The statistic analysis of effects of tau overexpression the decay time constant at +60 mV (n = 9). *P>0.05 compared with control.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4295873&req=5

pone.0116628.g004: Overexpression of tau inhibited whole-cell currents through Kv channels.(A) The outward Kv currents were evoked by stepped up to +60 mV for 500 ms at a holding potential of -80 mV in N2A cells. (B) These Kv currents were substantially decreased after tau transfection for 48 h. (C) Current–voltage (I-V) relations of outward Kv currents in the control (white circle) and transfection with tau (black circle). (D) The graph showed that statistic analysis of effects of tau overexpression on whole-cell Kv currents (n = 8). *P<0.05 compared with control. (E) Representative current traces in the absence and presence of tau overexpression. (F) The statistic analysis of effects of tau overexpression the decay time constant at +60 mV (n = 9). *P>0.05 compared with control.
Mentions: As a concomitant of decreased expression of Kv channels, the macroscopic currents through these channels should be declined after tau transfection. At a holding potential of -80 mV, the outward Kv currents in N2A cells were evoked by depolarization to testing potentials ranging from -80 mV to +60 mV (Fig. 4A). After transfection of N2A cells with tau for 48 h, the outward Kv currents appeared to be significantly declined at different testing potentials (Fig. 4B). In addition, the current–voltage curves (I–V), which were constructed by the data of current amplitudes measured at the various testing pulses, clearly showed the inhibitory effects of tau transfection on outward Kv currents (Fig. 4C). At +60 mV, overexpression of tau reduced currents from 564.3 ± 47.5 pA to 383.1 ± 55.8 pA (Fig. 4D). However, this treatment did not affect inward currents, even at -80 mV. To examine the effects of tau overexpression on the decay rate of outward Kv currents, whole-cell currents elicited during 5 s depolarizing voltage step to +60 mV from the holding potential of -80 mV were well fitted with a single exponential function. In the absence and presence of tau overexpression, the decay time constant τ at +60 mV were 2360.1 ± 131.3 ms and 2405.3 ± 192.6 ms, respectively (Fig. 4E, F). These results showed that tau induction unaffected the decay process of Kv currents (Fig. 4F).

Bottom Line: Furthermore, the macroscopic currents through Kv channels were reduced by 36.5% at +60 mV in tau-transfected N2A cells.Following the cotransfection with tau in HEK293 cells, the mRNA levels and corresponding currents of Kv2.1 were significantly declined compared with single Kv2.1 transfection.Our data indicated that overexpression of tau declined the mRNA levels of Kv channels and related currents.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, College of Life Sciences, South-Central University for Nationalities, Wuhan, 430074, China.

ABSTRACT
Microtubule binding protein tau has a crucial function in promoting the assembly and stabilization of microtubule. Besides tuning the action potentials, voltage-gated K+ channels (Kv) are important for cell proliferation and appear to play a role in the development of cancer. However, little is known about the possible interaction of tau with Kv channels in various tissues. In the present study, tau plasmids were transiently transfected into mouse neuroblastoma N2A cells to explore the possible linkages between tau and Kv channels. This treatment led to a downregulation of mRNA levels of several Kv channels, including Kv2.1, Kv3.1, Kv4.1, Kv9.2, and KCNH4, but no significant alteration was observed for Kv5.1 and KCNQ4. Furthermore, the macroscopic currents through Kv channels were reduced by 36.5% at +60 mV in tau-transfected N2A cells. The proliferation rates of N2A cells were also improved by the induction of tau expression and the incubation of TEA (tetraethylammonium) for 48 h by 120.9% and 149.3%, respectively. Following the cotransfection with tau in HEK293 cells, the mRNA levels and corresponding currents of Kv2.1 were significantly declined compared with single Kv2.1 transfection. Our data indicated that overexpression of tau declined the mRNA levels of Kv channels and related currents. The effects of tau overexpression on Kv channels provided an alternative explanation for low sensitivity to anti-cancer chemicals in some specific cancer tissues.

Show MeSH
Related in: MedlinePlus