Biomedical subjects

Roxanne K Barrow

Publications and source records attributed to Roxanne K Barrow.

6 recordsLinked to original sources

PubMed2006

DANGER, a novel regulatory protein of inositol 1,4,5-trisphosphate-receptor activity.

We report the cloning and characterization of DANGER, a novel protein which physiologically binds to inositol 1,4,5-trisphosphate receptors (IP(3)R). DANGER is a membrane-associated protein predicted to contain a partial MAB-21 domain. It is expressed in a wide variety of neuronal cell lineages where it localizes to membranes in the cell periphery together with IP(3)R. DANGER interacts with IP(3)R in vitro and co-immunoprecipitates with IP(3)R from cellular preparations. DANGER robustly enhances Ca(2+)-mediated inhibition of IP(3) RCa(2+) release without affecting IP(3) binding in microsomal assays and inhibits gating in single-channel recordings of IP(3)R. DANGER appears to allosterically modulate the sensitivity of IP(3) RtoCa(2+) inhibition, which likely alters IP(3)R-mediated Ca(2+) dynamics in cells where DANGER and IP(3)R are co-expressed.

Allosteric Site↗

PubMed2005

Phospholipase Cgamma1 controls surface expression of TRPC3 through an intermolecular PH domain.

Many ion channels are regulated by lipids, but prominent motifs for lipid binding have not been identified in most ion channels. Recently, we reported that phospholipase Cgamma1 (PLC-gamma1) binds to and regulates TRPC3 channels, components of agonist-induced Ca2+ entry into cells. This interaction requires a domain in PLC-gamma1 that includes a partial pleckstrin homology (PH) domain-a consensus lipid-binding and protein-binding sequence. We have developed a gestalt algorithm to detect hitherto 'invisible' PH and PH-like domains, and now report that the partial PH domain of PLC-gamma1 interacts with a complementary partial PH-like domain in TRPC3 to elicit lipid binding and cell-surface expression of TRPC3. Our findings imply a far greater abundance of PH domains than previously appreciated, and suggest that intermolecular PH-like domains represent a widespread signalling mode.

Algorithms↗

PubMed2005

Serine racemase: activation by glutamate neurotransmission via glutamate receptor interacting protein and mediation of neuronal migration.

Serine racemase (SR), localized to astrocytic glia that ensheathe synapses, converts L-serine to D-serine, an endogenous ligand of the NMDA receptor. We report the activation of SR by glutamate neurotransmission involving alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors via glutamate receptor interacting protein (GRIP) and the physiologic regulation of cerebellar granule cell migration by SR. GRIP physiologically binds SR, augmenting SR activity and D-serine release. GRIP infection of neonatal mouse cerebellum in vivo enhances granule cell migration. Selective degradation of D-serine by D-amino acid oxidase and pharmacologic inhibition of SR impede migration, whereas D-serine activates the process. Thus, in neuronal migration, glutamate stimulates Bergmann glia to form and release D-serine, which, together with glutamate, activates NMDA receptors on granule neurons, chemokinetically enhancing migration.

Animals↗

PubMed2005

Inositol 1,4,5-trisphosphate receptor/GAPDH complex augments Ca2+ release via locally derived NADH.

NADH regulates the release of calcium from the endoplasmic reticulum by modulation of inositol 1,4,5-trisphosphate receptors (IP3R), accounting for the augmented calcium release of hypoxic cells. We report selective binding of IP3R to GAPDH, whose activity leads to the local generation of NADH to regulate intracellular calcium signaling. This interaction requires cysteines 992 and 995 of IP3R and C150 of GAPDH. Addition of native GAPDH and NAD+ to WT IP3R stimulates calcium release, whereas no stimulation occurs with C992S/995S IP3R that cannot bind GAPDH. Thus, the IP3R/GAPDH interaction likely enables cellular energy dynamics to impact calcium signaling.

Animals↗

PubMed2004

Agonist-induced Ca2+ entry determined by inositol 1,4,5-trisphosphate recognition.

It has been considered that Ca2+ release is the causal trigger for Ca2+ entry after receptor activation. In DT40 B cells devoid of inositol 1,4,5-trisphosphate receptors (IP3R), the lack of Ca2+ entry in response to receptor activation is attributed to the absence of Ca2+ release. We reveal in this article that IP3R recognition of IP3 determines agonist-induced Ca2+ entry (ACE), independent of its Ca2+ release activity. In DT40 IP3R(-/-) cells, endogenous ACE can be rescued with type 1 IP3R mutants (both a DeltaC-terminal truncation mutant and a D2550A pore mutant), which are defective in Ca2+ release channel activity. Thus, in response to B cell receptor activation, ACE is restored in an IP3R-dependent manner without Ca2+ store release. Conversely, ACE cannot be rescued with mutant IP3Rs lacking IP3 binding (both the Delta90-110 and R265Q IP3-binding site mutants). We conclude that an IP3-dependent conformational change in the IP3R, not endoplasmic reticulum Ca2+ pool release, triggers ACE.

Amino Acid Substitution↗

PubMed2004

RACK1 binds to inositol 1,4,5-trisphosphate receptors and mediates Ca2+ release.

RACK1 is not a G protein but closely resembles the heterotrimeric Gbeta-subunit. RACK1 serves as a scaffold, linking protein kinase C to its substrates. We demonstrate that RACK1 physiologically binds inositol 1,4,5-trisphosphate receptors and regulates Ca2+ release by enhancing inositol 1,4,5-trisphosphate receptor binding affinity for inositol 1,4,5-trisphosphate. Overexpression of RACK1 or depletion of RACK1 by interference RNA markedly augments or diminishes Ca2+ release, respectively, without affecting Ca2+ entry. These findings establish RACK1 as a physiologic mediator of agonist-induced Ca2+ release.

Amino Acid Substitution↗