The plasma membrane Ca 2+ ATPase (PMCA) is responsible for maintaining basal intracellular Ca 2+ concentration ([Ca 2+] i) and returning small increases in [Ca 2+] i back to resting levels. The carboxyl terminus of some PMCA splice variants bind Homer proteins; how binding affects PMCA function is unknown. Here, we examined the effects of altered expression of Homer proteins on PMCA-mediated Ca 2+ clearance from rat hippocampal neurons in culture. The kinetics of PMCA-mediated recovery from the [Ca 2+] i increase evoked by a brief train of action potentials was determined in the soma of single neurons using indo-1-based photometry. Exogenous expression of Homer 1a, Homer 1c or Homer 2a did not affect PMCA function. However, shRNA mediated knockdown of Homer 1 slowed PMCA mediated Ca 2+ clearance by 28% relative to cells expressing non-silencing shRNA. The slowed recovery rate in cells expressing Homer 1 shRNA was reversed by expression of a short Homer 2 truncation mutant. These results indicate that constitutively expressed Homer proteins tonically stimulate PMCA function in hippocampal neurons. We propose a model in which binding of short or long Homer proteins to the carboxyl terminus of the PMCA stimulates Ca 2+ clearance rate. PMCA-mediated Ca 2+ clearance may be stimulated following incorporation of the pump into Homer organized signaling domains and following induction of the Homer 1a immediate early gene.
|Original language||English (US)|
|Number of pages||6|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Jul 20 2012|
Bibliographical noteFunding Information:
The National Science Foundation [Grant IOS0814549 ] and the National Institute on Drug Abuse [Grants DA07304 and DA11806 ] supported this work.
- Ca signaling
- Hippocampal neuron
- PDZ domain