Nuclear sequestration of β-subunits by Rad and Rem is controlled by 14-3-3 and calmodulin and reveals a novel mechanism for Ca2+ channel regulation

P Béguin, RN Mahalakshmi, K Nagashima… - Journal of molecular …, 2006 - Elsevier
P Béguin, RN Mahalakshmi, K Nagashima, DHK Cher, H Ikeda, Y Yamada, Y Seino…
Journal of molecular biology, 2006Elsevier
Voltage-gated Ca2+ channels (VDCCs) are heteromultimeric proteins that mediate Ca2+
influx into cells upon membrane depolarization. These channels are involved in various
cellular events, including gene expression, regulation of hormone secretion and synaptic
transmission. Kir/Gem, Rad, Rem, and Rem2 belong to the RGK family of Ras-related small
G proteins. RGK proteins interact with the β-subunits and downregulate VDCC activity.
Kir/Gem was proposed to prevent surface expression of functional Ca2+ channels, while for …
Voltage-gated Ca2+ channels (VDCCs) are heteromultimeric proteins that mediate Ca2+ influx into cells upon membrane depolarization. These channels are involved in various cellular events, including gene expression, regulation of hormone secretion and synaptic transmission. Kir/Gem, Rad, Rem, and Rem2 belong to the RGK family of Ras-related small G proteins. RGK proteins interact with the β-subunits and downregulate VDCC activity. Kir/Gem was proposed to prevent surface expression of functional Ca2+ channels, while for Rem2 the mechanism remains controversial. Here, we have analyzed the mechanism by which Rad and Rem regulate VDCC activity. We show that, similar to Kir/Gem and Rem2, 14-3-3 and CaM binding regulate the subcellular distribution of Rad and Rem, which both inhibit Ca2+ channel activity by preventing its expression on the cell surface. This function is regulated by calmodulin and 14-3-3 binding only for Rad and not for Rem. Interestingly, nuclear targeting of Rad and Rem can relocalize and sequester the β-subunit to the nucleus, thus providing a novel mechanism for Ca2+ channel downregulation.
Elsevier