Characterization of the Human Sigma-1 Receptor Chaperone Domain Structure and Binding Immunoglobulin Protein (BiP) Interactions

Proc. Natl. Acad. Sci. U.S.A.

Pokrass

Klauer

et al. 2015

Dysregulation of cyclin-dependent kinase 5 (cdk5) per relative concentrations of its activators p35 and p25 is implicated in neurodegenerative diseases. P35 has a short t ½ and undergoes rapid proteasomal degradation in its membrane-bound myristoylated form. P35 is converted by calpain to p25, which, along with an extended t ½ , promotes aberrant activation of cdk5 and causes abnormal hyperphosphorylation of tau, thus leading to the formation of neurofibrillary tangles. The sigma-1 receptor (Sig-1R) is an endoplasmic reticulum chaperone that is implicated in neuronal survival. However, the specific role of the Sig-1R in neurodegeneration is unclear. Here we found that Sig-1Rs regulate proper tau phosphorylation and axon extension by promoting p35 turnover through the receptor's interaction with myristic acid. In Sig-1R-KO neurons, a greater accumulation of p35 is seen, which results from neither elevated transcription of p35 nor disrupted calpain activity, but rather to the slower degradation of p35. In contrast, Sig-1R overexpression causes a decrease of p35. Sig-1R-KO neurons exhibit shorter axons with lower densities. Myristic acid is found here to bind Sig-1R as an agonist that causes the dissociation of Sig-1R from its cognate partner binding immunoglobulin protein. Remarkably, treatment of Sig-1R-KO neurons with exogenous myristic acid mitigates p35 accumulation, diminishes tau phosphorylation, and restores axon elongation. Our results define the involvement of Sig-1Rs in neurodegeneration and provide a mechanistic explanation that Sig-1Rs help maintain proper tau phosphorylation by potentially carrying and providing myristic acid to p35 for enhanced p35 degradation to circumvent the formation of overreactive cdk5/p25.A xons are structurally and functionally distinct protrusions of neurons that modulate neurotransmitter release and neural function. Malfunction of axonal maintenance, regeneration, and target recognition contribute to CNS disorders such as Alzheimer's disease (AD), Parkinson's disease, stroke, and spinal cord injuries (1-3). Cyclin-dependent kinase (Cdk) 5 activities within the axon play a significant role in the cytoskeletal dynamics of microtubules and actin neurofilaments (NFs), which determine axonal path and length. Specifically, cdk5 active complexes phosphorylate proteins that contribute to the stabilization or destabilization of microtubules, formation of neurofibrillary tangles, and axonal pathfinding (4-6).Cdk5 is a ubiquitously expressed enzyme; however, its activator, p35, is almost exclusively expressed in neurons (7,8). Cdk5 signaling supports neurite projection and proper neuronal migration (9-11). Dysregulation of cdk5 activity leads to hyperphosphorylation of several substrates, including NF proteins and tau, which causes the formation of neurofibrillary tangles (6, 12). Although the kinetics of cdk5 activity when in complex with p35 or p25 are the same, cdk5/p25 complexes are proposed to be responsible for neurodegenerative pathophysiology because of their longer duration o...

Section: Sig-1r Controls P35 Degradation Mainly Through the Proteasomalmentioning

confidence: 99%

Section: Sig-1r Controls P35 Degradation Mainly Through the Proteasomalmentioning

confidence: 99%

Section: Significancementioning

confidence: 99%

See 1 more Smart Citation

Sigma-1 receptor regulates Tau phosphorylation and axon extension by shaping p35 turnover via myristic acid

Proc. Natl. Acad. Sci. U.S.A.

Pokrass

Klauer

et al. 2015

“…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). However, the functional role of Sig1Rs at the nucleus remains unknown.…”

mentioning

confidence: 99%

“…The sigma-1 receptor (Sig-1R) (5)(6)(7)(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).…”

mentioning

confidence: 99%

Sigma-1 receptor mediates cocaine-induced transcriptional regulation by recruiting chromatin-remodeling factors at the nuclear envelope

Chuang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2015

115

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...

Chemistry & Biodiversity

Ligand‐Guided Investigation of a Series of Formamidine‐Based Thiuram Disulfides as Potential Dual‐Inhibitors of COX‐1and COX‐2

Oladipo

Akinpelu

Omondi

2022

A series of thiuram disulfides 1-6 which had been previously synthesized and characterized, [1] were studied for their potential therapeutic properties. Target-fishing analyses through HitPick and SwissTarget prediction identified COX1 and COX2, which are essential biomolecules in cancer-related inflammations, as the possible targets for compounds 1 and 4 among all the compounds tested. These two proteins have enjoyed interest as targets for treating some neoplastic cancer types such as breast, colorectal, skin, pancreatic, haematological and head cancers. The inhibitory potency of 1 and 4 as lead anticancer drug candidates with dual-target ability against COX1 and COX2 was examined through molecular docking, molecular dynamics simulation and post-MD analyses such as binding energy calculation, RMSD, RMSF, and RoG. The two compounds had better docking scores and binding energies than the known inhibitors of COX1 and COX2. Insights from the RMSD, RMSF, and RoG suggested that both 1 and 4 showed observable influence on the structural stability of these targets throughout the simulation. The reported observations of the effects of 1 and 4 on the structures of COX1 and COX2 indicate their probable inhibitory properties against these target proteins and their potential as lead anticancer drug candidates.