Biomedical subjects

S Voglmaier

Publications and source records attributed to S Voglmaier.

3 recordsLinked to original sources

PubMed1997

Molecular characterization of a Dictyostelium G-protein alpha-subunit required for development.

Dictyostelium discoideum utilizes G-protein-regulated transmembrane signaling systems to implement its developmental program. This report describes the Dictyostelium G-protein alpha-subunit, G alpha3, and demonstrates that it is required for normal development. G alpha3 is the largest of the four completely sequenced Dictyostelium G-protein alpha-subunits. The difference in size is due to variability in the N-terminal regions. The regions which are affected by the increased size of G alpha3 are the Gbeta gamma binding region and the helical domain that protects the guanine nucleotide cleft. g alpha3- mutants created by gene disruption fail to aggregate. However, when treated with exogenous pulses of cAMP that mimic the endogenous cAMP oscillations, they are able to aggregate, but development arrests at the tipped mound stage. This conditional developmental phenotype suggests that G alpha3 is required for production of the cAMP signal.

Amino Acid Sequence↗

PubMed1989

High-affinity cannabinoid binding site: regulation by ions, ascorbic acid, and nucleotides.

The high-affinity cannabinoid site in rat brain is an integral component of brain membranes that recognizes cannabinoids with inhibitory constants (Ki) in the nanomolar range. To clarify its physiological role, we studied the regulation of [3H]5'-trimethylammonium delta 8-tetrahydrocannabinol ([3H]TMA) binding. The site is inhibited by heavy metal ions, such as La3+, at low micromolar concentrations; divalent cations, such as Ca2+ and Mg2+, inhibit [3H]TMA binding, though at somewhat higher concentrations. In contrast, [3H]TMA binding is stimulated by Fe2+, Cu2+, and Hg2+ ions. Ascorbic acid and its analogs are also stimulators of cannabinoid binding at low micromolar concentrations. Stimulation of [3H]TMA binding by ascorbate or ions is dependent upon molecular oxygen, but is not inhibited by metabolic poisons. Metabolically stable nucleoside triphosphate analogs enhance [3H]TMA binding by different mechanisms, with hydrolysis of a high-energy phosphate bond apparently requisite for these influences. These results suggest that the cannabinoid binding site is associated with a nucleotide-utilizing protein possessing multiple regulatory subsites.

Adenosine Triphosphate↗

PubMed1988

Myelin basic protein is an endogenous inhibitor of the high-affinity cannabinoid binding site in brain.

Radioligand binding studies with the water-soluble cannabinoid [3H]5'-trimethylammonium delta 8-tetrahydrocannabinol ([3H]TMA) have revealed a saturable high-affinity site in brain that is specific for cannabinoids. To determine whether endogenous compounds of brain might act upon the site physiologically, we sought inhibitors in extracts of brain. An endogenous inhibitor has been purified to homogeneity by acid extraction of rat brain followed by adsorption to a reverse-phase matrix and gel filtration chromatography. The purified inhibitor has a subunit molecular mass of 14,500 daltons by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Inhibition of [3H]TMA binding by the purified inhibitor occurs with a Ki of about 4 nM in a noncompetitive manner. The molecular weight, abundance, and extraction properties are the same as a species of myelin basic protein (MBP). The MBPs of rat, rabbit, pig, and cow also inhibit [3H]TMA binding noncompetitively with similar potencies. The purified inhibitor comigrates with rat MBP-small form on SDS-PAGE, has a similar amino acid composition, and is recognized by antibody directed against MBP. Studies of fragments of rabbit MBP suggest that the determinants of affinity for the [3H]TMA site are contained primarily within the C-terminal half of the rabbit MBP. Synthetic polycationic peptides such as polylysine and polyarginine mimic the effects of MBP, suggesting that the high-affinity cannabinoid binding site recognizes large polycations. The identification of the endogenous inhibitor of [3H]TMA binding as MBP suggests that MBP interacts physiologically with the high-affinity cannabinoid site.

Amino Acids↗