We found that host heat shock proteins Hsp70 and Hsp90 are required for RCNMV RNA replication and that they interact with p27, a virus-encoded component
of the 480-kDa replicase complex, on the endoplasmic reticulum membrane. Using a cell-free viral translation/replication system in combination with specific inhibitors of Hsp70 and Hsp90, we found that inhibition of p27-Hsp70 interaction inhibits the formation of the 480-kDa complex but instead induces the accumulation of large complexes that are nonfunctional in viral RNA synthesis. In BIBW2992 datasheet contrast, inhibition of p27-Hsp90 interaction did not induce such large complexes but rendered p27 incapable of binding to a specific viral RNA element, which is a critical step for the assembly of the 480-kDa replicase complex and viral RNA replication. Together, our results suggest that Hsp70 and Hsp90 regulate different steps in the assembly of the RCNMV replicase complex.”
“The h5-HT7 receptor is subject to inactivation by risperidone and 9-OH-risperidone, apparently through a pseudo-irreversible complex
formed between these drugs and the receptor. Although risperidone and 9-OH-risperidone (“”inactivating antagonists”") completely inactivate the receptor, only 50% of the receptors form a pseudo-irreversible complex with these drugs.
This study aims to more fully determine the mechanism(s) responsible for the novel effects of risperidone and 9-OH-risperidone and to determine if the inactivation can be reversed (reactivation).
The ability of non-inactivating drugs (competitive antagonists) to dissociate wash-resistant [H-3]risperidone cAMP activator inhibitor binding from h5-HT7 receptors was investigated. Leukotriene-A4 hydrolase Also, the ability of non-inactivating drugs to reactivate inactivated h5-HT7 receptors was investigated, using cAMP accumulation as a functional endpoint.
The competitive (non-inactivating) antagonists clozapine and mesulergine released the wash-resistant [H-3]risperidone binding to the h5-HT7 receptor. The competitive antagonists clozapine, SB269970, mianserin, cyproheptadine, mesulergine, and ICI169369 reactivated the risperidone-inactivated h5-HT7 receptors in a concentration-dependent
manner. The potencies for reactivation closely match the affinities of these drugs for the h5-HT7 receptor (r (2) = 0.95), indicating that the reactivating antagonists are binding to and producing their effects through the orthosteric binding site of the h5-HT7 receptor. Bioluminescence resonance energy transfer analyses indicate that the h5-HT7 receptor forms homodimers.
The ability of the non-inactivating drugs to bind h5-HT7 orthosteric sites and reverse the wash-resistant effects of risperidone or 9-OH-risperidone, also bound to h5-HT7 orthosteric sites, is evidence for protomer-protomer interactions between h5-HT7 homodimers. This is the first demonstration of a non-mutated G-protein-coupled receptor homodimer engaging in protomer-protomer interactions in an intact cell preparation.