Summary The sigma-1 receptor (Sig-1R), an endoplasmic reticulum (ER) chaperone protein, is an inter-organelle signaling modulator that potentially plays a role in drug-seeking behaviors. However, the brain site of action and underlying cellular mechanisms remain unidentified. We found that cocaine exposure triggers a Sig-1R-dependent upregulation of D-type K+ current in the nucleus accumbens (NAc) that results in neuronal hypoactivity, and thereby enhances behavioral cocaine response. Combining ex vivo and in vitro studies, we demonstrated that this neuroadaptation is caused by a persistent protein-protein association between Sig-1Rs and Kv1.2 channels, a phenomenon that is associated to a redistribution of both proteins from intracellular compartments to the plasma membrane. In conclusion, the dynamic Sig-1R - Kv1.2 complex represents a novel mechanism that shapes neuronal and behavioral response to cocaine. Functional consequences of Sig-1R binding to K+ channels may have implications for other chronic diseases where maladaptive intrinsic plasticity and Sig-1Rs are engaged.

The sigma-1 receptor (Sig-1R) chaperone at the endoplasmic reticulum (ER) plays important roles in cellular regulation. Here we found a new function of Sig-1R, in that it translocates from the ER to the nuclear envelope (NE) to recruit chromatin-remodeling molecules and regulate the gene transcription thereof. Sig-1Rs mainly reside at the ER-mitochondrion interface. However, on stimulation by agonists such as cocaine, Sig-1Rs translocate from ER to the NE, where Sig-1Rs bind NE protein emerin and recruit chromatin-remodeling molecules, including lamin A/C, barrier-to-autointegration factor (BAF), and histone deacetylase (HDAC), to form a complex with the gene repressor specific protein 3 (Sp3). Knockdown of Sig-1Rs attenuates the complex formation. Cocaine was found to suppress the gene expression of monoamine oxidase B (MAOB) in the brain of wild-type but not Sig-1R knockout mouse. A single dose of cocaine (20 mg/kg) in rats suppresses the level of MAOB at nuclear accumbens without affecting the level of dopamine transporter. Daily injections of cocaine in rats caused behavioral sensitization. Withdrawal from cocaine in cocaine-sensitized rats induced an apparent time-dependent rebound of the MAOB protein level to about 200% over control on day 14 after withdrawal. Treatment of cocaine-withdrawn rats with the MAOB inhibitor deprenyl completely alleviated the behavioral sensitization to cocaine. Our results demonstrate a role of Sig-1R in transcriptional regulation and suggest cocaine may work through this newly discovered genomic action to achieve its addictive action. Results also suggest the MAOB inhibitor deprenyl as a therapeutic agent to block certain actions of cocaine during withdrawal.T he endoplasmic reticulum (ER) plays important roles in cellular functions, including synthesis of proteins and regulation of Ca 2+ signaling between the ER and plasma membrane (1) and between the ER and mitochondria (2-4). However, because the ER interacts with other organelles in the cell, other functions related to the ER remain to be uncovered.The sigma-1 receptor (Sig-1R) (5-8) is an ER chaperone molecule that resides at the ER-mitochondrion interface referred to as the mitochondria-associated ER membrane (MAM), where the Sig-1R ensures proper ER-mitochondrion Ca 2+ signaling for cellular survival (3, 9), as well as sustains the activity of an ER stress sensor IRE1 at the MAM (10). The Sig-1R can translocate from the MAM to plasma membrane of the cell to regulate ion channels and receptors on the plasma membrane (8,(11)(12)(13)(14). Cocaine is a Sig-1R agonist (3) that causes the dissociation of Sig-1R from its cognate binding partner BiP (3,8), and consequently the translocation of Sig-1Rs to the plasma membrane, where Sig-1Rs interact with voltage-gated potassium channel subfamily A member 2 (Kv1.2) to shape the neuronal and behavioral responses to cocaine (15).Cocaine also causes the translocation of Sig-1Rs from the ER to the nucleus (16), where Sig-1Rs are shown to be present at the nuclear envelope (NE) (17). H...

SUMMARY Human pluripotent stem cell (hPSC) lines exhibit repeated patterns of genetic variation, which can alter in vitro properties as well as suitability for clinical use. We examined associations between copy number variations (CNVs) on chromosome 17 and hPSC mesodiencephalic dopaminergic (mDA) differentiation. Among 24 hPSC lines, two karyotypically-normal lines, BG03 and CT3, and BG01V2, with trisomy 17, exhibited amplification of the WNT3/WNT9B region and rapid mDA differentiation. In hPSC lines with amplified WNT3/WNT9B, bFGF signaling through MAPK/ERK amplifies canonical WNT signaling by phosphorylating LRP6, resulting in enhanced undifferentiated proliferation. When bFGF is absent, non-canonical WNT signaling becomes dominant due to up-regulation of SIAH2, enhancing JNK signaling and promoting loss of pluripotency. When bFGF is present during mDA differentiation, stabilization of canonical WNT signaling causes up-regulation of LMX1A and mDA induction. Therefore CNVs in 17q21.31, a “hot spot” for genetic variation, have multiple and complex effects on hPSC cellular phenotype.