TY  - JOUR
A1  - Böhm, J.
A1  - Scherzer, S.
A1  - Shabala, S.
A1  - Krol, E.
A1  - Neher, E.
A1  - Mueller, T. D.
A1  - Hedrich, R.
T1  - Venus flytrap HKT1-type channel provides for prey sodium uptake into carnivorous plant without conflicting with electrical excitability
JF  - Molecular Plant
N2  - The animal diet of the carnivorous Venus flytrap, Dionaea muscipula, contains a sodium load that enters the capture organ via an HKT1-type sodium channel, expressed in special epithelia cells on the inner trap lobe surface. DmHKT1 expression and sodium uptake activity is induced upon prey contact. Here, we analyzed the HKT1 properties required for prey sodium osmolyte management of carnivorous Dionaea. Analyses were based on homology modeling, generation of model-derived point mutants, and their functional testing in Xenopus oocytes. We showed that the wild-type HKT1 and its Na\(^+\)- and K\(^+\)-permeable mutants function as ion channels rather than K\(^+\) transporters driven by proton or sodium gradients. These structural and biophysical features of a high-capacity, Na\(^+\)-selective ion channel enable Dionaea glands to manage prey-derived sodium loads without confounding the action potential-based information management of the flytrap.
KW  - sodium channel
KW  - HKT1
KW  - Dionaea muscipula
KW  - action potential
KW  - glands
KW  - sodium uptake
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-189803
VL  - 9
IS  - 3
ER  - 
TY  - JOUR
A1  - Wetzel, Andrea
A1  - Jablonka, Sibylle
A1  - Blum, Robert
T1  - Cell-autonomous axon growth of young motoneurons is triggered by a voltage-gated sodium channel
JF  - Channels (Austin)
N2  - Spontaneous electrical activity preceding synapse formation contributes to the precise regulation of neuronal development. Examining the origins of spontaneous activity revealed roles for neurotransmitters that depolarize neurons and activate ion channels. Recently, we identified a new molecular mechanism underlying fluctuations in spontaneous neuronal excitability. We found that embryonic motoneurons with a genetic loss of the low-threshold sodium channel Na\(_V\)1.9 show fewer fluctuations in intracellular calcium in axonal compartments and growth cones than wild-type littermates. As a consequence, axon growth of Na\(_V\)1.9-deficient motoneurons in cell culture is drastically reduced while dendritic growth and cell survival are not affected. Interestingly, Na\(_V\)1.9 function is observed under conditions that would hardly allow a ligand- or neurotransmitter-dependent depolarization. Thus, Na\(_V\)1.9 may serve as a cell-autonomous trigger for neuronal excitation. In this addendum, we discuss a model for the interplay between cell-autonomous local neuronal activity and local cytoskeleton dynamics in growth cone function.
KW  - spontaneous excitation
KW  - spinal muscular atrophy
KW  - axon growth
KW  - sodium channel
KW  - motoneurons
KW  - local protein synthesis
KW  - NaV1.9
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-132586
VL  - 7
IS  - 1
ER  -