title: Homer proteins mediate the interaction between STIM1 and Cav1.2 channels.
abstract: STIM1 is a ubiquitous Ca2+ sensor of the intracellular, agonist-sensitive, Ca2+ stores that communicates the filling state of the Ca2+ compartments to plasma membrane store-operated Ca2+ (SOC) channels. STIM1 has been presented as a point of convergence between store-operated and voltage-operated Ca2+ influx, both inducing activation of SOC channels while suppressing Cav1.2 channels. Here we report that Homer proteins play a relevant role in the communication between STIM1 and Cav1.2 channels. HEK-293 cells transiently expressing Cav1.2 channel subunits α1, β2 and α2δ-1 exhibited a significant Ca2+ entry upon treatment with a high concentration of KCl. In Cav1.2-expressing cells, treatment with thapsigargin (TG), to induce passive discharge of the intracellular Ca2+ stores, resulted in Ca2+ influx that was significantly greater than in cells not expressing Cav1.2 channels, a difference that was abolished by nifedipine and diltiazem. Treatment with TG induces co-immunoprecipitation of Homer1 with STIM1 and the Cav1.2 α1 subunit. Impairment of Homer function by introduction of the synthetic PPKKFR peptide into cells, which emulates the proline-rich sequences of the PPXXF motif, or using siRNA Homer1, reduced the association of STIM1 and the Cav1.2 α1 subunit. These findings indicate that Homer is important for the association between both proteins. Finally, treatment with siRNA Homer1 or the PPKKFR peptide enhanced the nifedipine-sensitive component of TG response in Cav1.2-expressing cells. Altogether, these findings provide evidence for a new role of Homer1 supporting the regulation of Cav1.2 channels by STIM1.
authors.affiliation: Department of Physiology (Cell Physiology Research Group), University of Extremadura, 10003 Cáceres, Spain.
authors.forename: Natalia
authors.initials: N
authors.lastname: Dionisio
authors.affiliation: Department of Medical Physiology and Biophysic, Institute of Biomedicine of Sevilla, Sevilla, Spain.
authors.forename: Tarik
authors.initials: T
authors.lastname: Smani
authors.affiliation: Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Woodard
authors.affiliation: Department of Medical Physiology and Biophysic, Institute of Biomedicine of Sevilla, Sevilla, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Castellano
authors.affiliation: Department of Physiology (Cell Physiology Research Group), University of Extremadura, 10003 Cáceres, Spain.
authors.forename: Gines M
authors.initials: GM
authors.lastname: Salido
authors.affiliation: Department of Physiology (Cell Physiology Research Group), University of Extremadura, 10003 Cáceres, Spain. Electronic address: jarosado@unex.es.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Rosado
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004110:Diltiazem / Q000494:pharmacology; D057809:HEK293 Cells; D000072233:Homer Scaffolding Proteins; D006801:Humans; D047468:Immunoprecipitation; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D021122:Protein Subunits / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D002352:Carrier Proteins; C000606614:HOMER1 protein, human; D000072233:Homer Scaffolding Proteins; C000606624:Homer1 protein, rat; C419385:L-type calcium channel alpha(1C); D008565:Membrane Proteins; D009363:Neoplasm Proteins; D010455:Peptides; D021122:Protein Subunits; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D019284:Thapsigargin; D004110:Diltiazem; D009543:Nifedipine; D002118:Calcium
keywords: Ca(2+) entry; Ca(v)1.2 channels; Homer1; Nifedipine; Protein–protein interactions; STIM1