Browsing by Author "Rehak, Renata"

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    Glutamate receptors on myelinated spinal cord axons: I. GluR6 kainate receptors
    (Wiley-Liss, Inc., 2009-02) Ouardouz, Mohamed; Basak, Ajoy; Chen, Andrew; Rehak, Renata; Yin, Xinghua; Coderre, Elaine M.; Zamponi, Gerald W.; Hameed, Shahid; Trapp, Bruce D. T.; Stys, Peter K.
    The deleterious effects of glutamate excitotoxicity are well described for central nervous system gray matter. Although overactivation of glutamate receptors also contributes to axonal injury, the mechanisms are poorly understood. Our goal was to elucidate the mechanisms of kainate receptor-dependent axonal Ca(2+) deregulation.
  • Thumbnail Image
    ItemOpen Access
    Identification of a molecular gating determinant within the carboxy terminal region of Cav3.3 T-type channels
    (2019-04-08) Jurkovicova-Tarabova, Bohumila; Cmarko, Leos; Rehak, Renata; Zamponi, Gerald W; Lacinova, Lubica; Weiss, Norbert
    Abstract The physiological functions controlled by T-type channels are intrinsically dependent on their gating properties, and alteration of T-type channel activity is linked to several human disorders. Therefore, it is essential to develop a clear understanding of the structural determinants responsible for the unique gating features of T-type channels. Here, we have investigated the specific role of the carboxy terminal region by creating a series a deletion constructs expressed in tsA-201 cells and analyzing them by patch clamp electrophysiology. Our data reveal that the proximal region of the carboxy terminus contains a structural determinant essential for shaping several gating aspects of Cav3.3 channels, including voltage-dependence of activation and inactivation, inactivation kinetics, and coupling between the voltage sensing and the pore opening of the channel. Altogether, our data are consistent with a model in which the carboxy terminus stabilizes the channel in a closed state.
  • Thumbnail Image
    ItemOpen Access
    Intermediate conductance calcium-activated potassium channels modulate summation of parallel fiber input in cerebellar Purkinje cells
    (Proceedings of the National Academy of Sciences, 2012-02-14) Engbers, Jordan D .T.; Anderson, Dustin M.; Asmara, Hadhimulya; Rehak, Renata; Mehaffey, W. Hamish; Hameed, Shahid; McKay, Bruce E.; Kruskic, Mirna; Zamponi, Gerald W.; Turner, Ray W.
    Encoding sensory input requires the expression of postsynaptic ion channels to transform key features of afferent input to an appropriate pattern of spike output. Although Ca(2+)-activated K(+) channels are known to control spike frequency in central neurons, Ca(2+)-activated K(+) channels of intermediate conductance (KCa3.1) are believed to be restricted to peripheral neurons. We now report that cerebellar Purkinje cells express KCa3.1 channels, as evidenced through single-cell RT-PCR, immunocytochemistry, pharmacology, and single-channel recordings. Furthermore, KCa3.1 channels coimmunoprecipitate and interact with low voltage-activated Cav3.2 Ca(2+) channels at the nanodomain level to support a previously undescribed transient voltage- and Ca(2+)-dependent current. As a result, subthreshold parallel fiber excitatory postsynaptic potentials (EPSPs) activate Cav3 Ca(2+) influx to trigger a KCa3.1-mediated regulation of the EPSP and subsequent after-hyperpolarization. The Cav3-KCa3.1 complex provides powerful control over temporal summation of EPSPs, effectively suppressing low frequencies of parallel fiber input. KCa3.1 channels thus contribute to a high-pass filter that allows Purkinje cells to respond preferentially to high-frequency parallel fiber bursts characteristic of sensory input.
  • Thumbnail Image
    ItemOpen Access
    T-type channel interactions with calcium activated potassium channels
    (2012-10-03) Rehak, Renata; Zamponi, Gerald
    In this thesis we investigate the relationship between calcium activated potassium channels (KCa1.1, KCa3.1) and low voltage activated calcium channels (Cav3). KCa1.1 are known to participate in neuronal excitability through their contribution to action potential repolarization and generation of fast afterhyperpolarizing potentials (AHPs) whereas KCa3.1 channels contribute to slow AHPs. Although both KCa channel isoforms have previously been shown to be activated by calcium influx through high voltage activated calcium channels their association with Cav3 channels is unknown. First, we show that Cav3 channels are able to activate KCa1.1 channels in medial vestibular neurons and this activation takes on the voltage profile of Cav3 channels, generating KCa1.1 currents at much lower voltages than previously described for the KCa1.1-HVA complex. Using tsA-201 cells, we further characterize this relationship and show that calcium influx through Cav3.2 greatly potentiates KCa1.1 current and shifts KCa1.1 activation to hyperpolarized potentials. We also find that this complex functions in a microdomain even though the two channels are able to co-immunoprecipitate. We narrowed down the site of interaction for Cav3.2 channels on KCa1.1 as transmembrane segment S0 which has previously been shown to be involved in the binding of the KCa1.1 auxiliary β4 subunit. Surprisingly, further investigation revealed that β4 subunit is also able to bind to Cav3.2 channels and functionally decreases Cav3 current density as well as shift its activation to more positive potentials. Also, when β4 is in a complex with KCa1.1 and Cav3.2, it negates the shift in KCa1.1 activation by Cav3.2. Finally, we show that the KCa3.1 channels which previously were not thought to participate in regulating the excitability of neurons in the CNS are present in Purkinje cells and contribute to the AHP in these cells. Furthermore, we show that Cav3 channels are able to activate these KCa3.1 channels and confer a voltage dependence to their activation based on the amount of calcium influx through Cav3.We further show that these two channels physically bind through multiple sites of interaction. This work generates a new role for the activation of KCa1.1 and KCa3.1 by Cav3.