Fine-tuning of GPCR signals by intracellular G protein modulators.

Heterotrimeric G proteins convey receptor signals to intracellular effectors. Superimposed over the basic GPCR-G protein-effector scheme are three types of auxiliary proteins that also modulate Gα. Regulator of G protein signaling proteins and G protein signaling modifier proteins respectively promote GTPase activity and hinder GTP/GDP exchange to limit Gα activation.

Functional comparison of full-length and N-terminal-truncated octopamine transporters from Lepidoptera.

We have cloned two new lepidopteran octopamine transporters (OATs), members of the solute-linked carrier family 6 (SLC6) of nutrient transporters, from the CNS of the European corn borer Ostrinia nubilalis and the cabbage white Pieris rapae. Comparison of these sequences with the previously cloned OAT from the cabbage looper Trichoplusia ni showed that the T. ni OAT sequence previously reported was truncated by 74 amino acids at the N-terminus.

Ancestry of neuronal monoamine transporters in the Metazoa.

Selective Na(+)-dependent re-uptake of biogenic monoamines at mammalian nerve synapses is accomplished by three types of solute-linked carrier family 6 (SLC6) membrane transporter with high affinity for serotonin (SERTs), dopamine (DATs) and norepinephrine (NETs). An additional SLC6 monoamine transporter (OAT), is responsible for the selective uptake of the phenolamines octopamine and tyramine by insect neurons. We have characterized a similar high-affinity phenoloamine transporter expressed in the CNS of the earthworm Lumbricus terrestris.

Novel activity of RGS14 on Goalpha and Gialpha nucleotide binding and hydrolysis distinct from its RGS domain and GDI activity.

The bifunctional protein RGS14 is both a GTPase activating protein (GAP) for Gialpha and Goalphaand a guanine nucleotide dissociation inhibitor (GDI) for Gialpha. This GDI activity is isolated to a region of the protein distinct from the RGS domain that contains an additional G protein-binding domain (RBD/GL). Here, we report that RGS14 missing its RGS domain (R14-RBD/GL) binds directly to Go and Gi to modulate nucleotide binding and hydrolysis by mechanisms distinct from its defined GDI activity.

RGS2 binds directly and selectively to the M1 muscarinic acetylcholine receptor third intracellular loop to modulate Gq/11alpha signaling.

RGS proteins serve as GTPase-activating proteins and/or effector antagonists to modulate Galpha signaling events. In live cells, members of the B/R4 subfamily of RGS proteins selectively modulate G protein signaling depending on the associated receptor (GPCR). Here we examine whether GPCRs selectively recruit RGS proteins to modulate linked G protein signaling.

Characterization and comparison of RGS2 and RGS4 as GTPase-activating proteins for m2 muscarinic receptor-stimulated G(i).

RGS2 and RGS4 were studied for their effects as GTPase activating proteins (GAPs) on receptor-activated G(i) in a novel steady-state assay using membranes from Sf9 cells quadruply infected with baculoviruses encoding the m2 muscarinic receptor, G(alphai2), G(beta1), and G(gamma2). In the presence of the muscarinic agonist carbachol, regulator of G protein signaling 2 (RGS2) and RGS4 each produced up to a 10-fold increase in agonist-dependent GTPase activity. The observed K(m) for GTP in this system was increased in the presence of RGS4.