Modulation of neuronal voltage-gated calcium channels by kelch-like-1 protein

PERISSINOTTI PP; ETHINGTON EG; CRIBBS L; HE Y; MARTIN J; KOOB MD; PIEDRAS-RENTERÍA ES

Chicago

Congreso; Chicago Chapter of the Society for Neuroscience 2014 Scientific Meeting; 2014

Kelch-like 1 protein (KLHL-1) is an actin-binding protein specific to the nervous system, constitutively expressed throughout the cytoplasm, axons and dendrites in neurons and in glia. The KLHL1 gene locus is closely localized to ATXN8 and in antisense to ATXN8OS, two genes implicated in the neurodegenerative disease Spinocerebellar ataxia type 8. This disease is characterized by the presence of trinucleotide expansions in the ATXN8OS and ATXN8 loci. It is not yet clear whether ATXN8OS alters KLHL1 expression or if the presence of expansions in this region affects KLHL1 function, however the expression pattern of the KLHL1 antisense strand is suggestive of a regulatory role of KLHL1, and also correlates with the pathology of SCA8. Moreover, trans-RNA interference assays in HEK 293 cells also suggest ATXN8OS may function as a negative regulator of KLHL1; furthermore, the conditional knockout model of KLHL1 exhibits loss of post-synaptic structures, mild cerebellar atrophy and loss of motor coordination and gait abnormalities, confirming a role of KLHL1 in normal cerebellar function. KLHL1 has various functions, including the modulation of neurite outgrowth and of ion channel activity in vitro. The positive modulation of voltage-gated calcium channels by KLHL-1 known to date includes CaV2.1 (P/Q-type, alpha 1A), 3.2 (T-type alpha 1H) but not 3.1 (T-type alpha 1G). In vitro studies revealed the ABP interacts with and up-regulates T-type alpha 1H calcium channel function by altering its kinetics of deactivation and by increasing the number of active channels present at the plasma membrane. The latter is achieved by the interaction of alpha 1H with KLHL-1 and with the polymerized actin cytoskeleton, which results in altered endosomal recycling, increased trafficking of alpha 1H back to the membrane and subsequent surface expression. Here we probed the endogenous effect of KLHL1 in KLHL1 KO mice, and compared it to the acute down-regulation using adenoviral delivery of shKLHL1 (gene knockdown) in WT neurons. Our results confirm that KLHL1 is a voltage-gated calcium channel modulator in cultured hippocampal and hypothalamic neurons, and shows that KLHL1 physiological role is not restricted to the cerebellum, where it is most abundant but it contributes to cellular function in all neuronal regions where it is expressed. Our data also suggests possible alterations in ion channel expression and/or compensatory changes may occur in the KLHL1. Supported by NSF.