ABSTRACT
Store-operated channels activated in response to intracellular calcium store depletion represent the main pathway of calcium entry from the extracellular space in nonelectroexcitable cells. Adapter proteins organize the components of this system into integral complex. We studied the influence of adapter proteins of the Homer family on endogenous store-operated calcium Imin channels in A431 cells. Monomeric Homer 1a proteins increase activity of Imin channels, but did not modulate their electrophysiological properties. Recombinant Homer 1c protein did not block the induced calcium currents.
Subject(s)
Calcium Channels/metabolism , Calcium/metabolism , Homer Scaffolding Proteins/physiology , Action Potentials/drug effects , Calcium Channel Agonists/metabolism , Calcium Channel Agonists/pharmacology , Calcium Channels/drug effects , Calcium Channels/physiology , Calcium Signaling/drug effects , Cytoplasm/metabolism , Electrophysiological Phenomena/drug effects , Homer Scaffolding Proteins/pharmacology , Humans , Ion Channel Gating/drug effects , Patch-Clamp Techniques , Protein Multimerization/physiology , Recombinant Proteins/pharmacology , Tumor Cells, CulturedABSTRACT
We have shown that the expression of full-length mutated huntingtin in human neuroblastoma cells (SK-N-SH) leads to an abnormal increase in calcium entry through store-operated channels. In this paper, the expression of the N-terminal fragment of mutated huntingtin (Htt138Q-1exon) is shown to be enough to provide an actual model for Huntington's disease. We have shown that Htt138Q-1exon expression causes increased store-operated calcium entry, which is mediated by at least two types of channels in SK-N-SH cells with different reversal potentials. Calcium sensor, STIM1, is required for activation of store-operated calcium entry in these cells. The results provide grounds for considering the proteins responsible for the activation and maintenance of the store-operated calcium entry as promising targets for developing novel therapeutics for neurodegenerative diseases.
Subject(s)
Calcium/metabolism , Carrier Proteins/metabolism , Neoplasm Proteins/metabolism , Neuroblastoma/metabolism , Neurotransmitter Agents/pharmacology , Peptides/pharmacology , Carrier Proteins/antagonists & inhibitors , Cell Line, Tumor , Homer Scaffolding Proteins , Humans , Neoplasm Proteins/antagonists & inhibitorsABSTRACT
Store-operated channels are major calcium influx pathways in nonexitable cells. Homer scaffold proteins are well known for their role in regulating calcium signaling. Here we report on a detailed single-channel level characterization of native store-operated channels regulated by Homer scaffold proteins in A431 carcinoma cells. By applying the single-channel patch-clamp technique, we found that different types of store-operated calcium channels have different sensitivities to Homer proteins.
