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Abstract：
Voltage-gated calcium (CaV) channels are responsible for Ca(2+) influx in excitable cells. As one of the auxiliary subunits, the CaV β subunit plays a pivotal role in the membrane expression and receptor modulation of CaV channels. In particular, the subcellular localization of the β subunit is critical for determining the biophysical properties of CaV channels. Recently, we showed that the β2e isotype is tethered to the plasma membrane. Such a feature of β2e is due to the reversible electrostatic interaction with anionic membrane phospholipids. Here, we further explored the membrane interaction property of β2e by comparing it with that of myristoylated alanine-rich C kinase substrate (MARCKS). First, the charge neutralization of the inner leaf of the plasma membrane induced the translocation of both β2e and MARCKS to the cytosol, while the transient depletion of poly-phosphoinositides (poly-PIs) by translocatable pseudojanin (PJ) systems induced the cytosolic translocation of β2e but not MARCKS. Second, the activation of protein kinase C (PKC) induced the translocation of MARCKS but not β2e. We also found that after the cytosolic translocation of MARCKS by receptor activation, depletion of poly-PIs slowed the recovery of MARCKS to the plasma membrane. Together, our data demonstrate that both β2e and MARCKS bind to the membrane through electrostatic interaction but with different binding affinity, and thus, they are differentially regulated by enzymatic degradation of membrane PIs.
摘要：
电压门控钙（CaV）通道负责可兴奋细胞中的Ca（2）流入。作为辅助子单位之一，CaVβ亚基在CaV通道的膜表达和受体调节中起关键作用。特别是,β亚基的亚细胞定位对于确定CaV通道的生物物理特性至关重要。最近,我们表明β2e同种型与质膜相连。β2e的这种特征是由于与阴离子膜磷脂的可逆静电相互作用。这里,通过与富含肉豆蔻酰化丙氨酸的C激酶底物（MARCKS）的比较，我们进一步探索了β2e的膜相互作用特性。首先,质膜内叶的电荷中和诱导了β2e和MARCKS向细胞质的易位，而可转位的假核蛋白（PJ）系统瞬时消耗聚磷酸肌醇（poly-PIs）会诱导β2e的胞浆易位，而不是MARCKS。第二,蛋白激酶C（PKC）的激活诱导了MARCKS的易位，而不是β2e的易位。我们还发现，通过受体激活MARCKS的胞浆易位后，poly-PI的消耗减慢了MARCKS向质膜的恢复。一起,我们的数据表明，β2e和MARCKS结合膜通过静电相互作用，但具有不同的结合亲和力，因此，它们受到膜PI的酶降解的差异调节。
