More specifically, this year’s breakthroughs include studies of ligand-receptor interactions, an unexpected mechanism of synaptic plasticity, a unique way to inhibit a kinase, insight into the consequences of cellular nutrient deprivation, and a quantitative analysis of the mitochondrial metabolome. Perhaps reflecting the growing maturity of the discipline of cellular signal transduction, many of this year’s nominations are relevant to the pathogenesis or have application to the treatment of human disease. Reth, B cell antigen receptors of the Ig M and Ig D classes are clustered in different protein islands that are altered during B cell activation. Faeder and Linding both nominated a study by Su )] that used an in vitro system with model membranes and 12 components of the TCR signaling pathway to explore the phosphorylation-dependent assembly of the transmembrane protein LAT (linker for activated T cells) and its binding partners.
In addition to providing insight into the physiological role of Pr P) both used computational approaches to discover either new drugs targeting the opioid receptor (A) or a new mechanism of inhibition of the kinase GSK-3 (B).
[Panel (A) is reprinted with permission from ) both used computational approaches to discover either new drugs targeting the opioid receptor (A) or a new mechanism of inhibition of the kinase GSK-3 (B).
As the name suggests, ubiquitin—and ubiquitination—is found in all eukaryotic cells and has been implicated in the regulation of nearly all cellular processes.
Ubiquitination involves a three-enzyme cascade, in which ubiquitin is activated by the E1 enzyme, in a process that requires ATP; activated ubiquitin is transferred to the E2 ubiquitin–conjugating enzyme and finally covalently linked to the substrate by the E3 ubiquitin ligase.
[Panel (A) is reprinted with permission from Like GPCRs, protein kinases are implicated in various disease states and are therefore promising targets for therapy. Samelson, The ability of Sos1 to oligomerize the adaptor protein LAT is separable from its guanine nucleotide exchange activity in vivo.
Excess activity of glycogen synthase kinase 3 (GSK-3) may contribute to various neurological disorders, including Alzheimer’s disease. In the CA1 region, where these processes have been extensively studied, LTP depends on an increase in the function of and localization of postsynaptic AMPA-type glutamate receptors (AMPARs), whereas LTD depends on decreased postsynaptic function and localization of AMPARs. In a study Hell described as “fascinating,” Sanderson -permeable AMPARs to the postsynaptic membrane. Like other protein kinases, however, developing an inhibitor that is both potent and selective has been a challenge. Kinase inhibitors that target the adenosine 5′-triphosphate (ATP) binding site tend to lack specificity, whereas competitive inhibitors derived from kinase substrates tend to be weak. Although prokaryotic signaling does not use ubiquitination, various bacterial pathogens have evolved effector proteins, including deubiquitinases and E3 ubiquitin ligases, that modulate ubiquitin signaling in their eukaryotic targets ( (nicotinamide adenine dinucleotide)–dependent ubiquitination process, in which ubiquitin undergoes adenosine 5′-diphosphate (ADP) ribosylation before its transfer to host Rab proteins. Following up on this surprising development, Bhogaraju ) determined that Sde A catalyzed the ubiquitination of target proteins on serine residues (rather than lysines, as in the classical ubiquitination pathway) and that ADP-ribosylated ubiquitin was converted to phosphoribosylated ubiquitin, which inhibited the eukaryotic polyubiquitination cascade. Two nominations concerned the application of insights into G protein–coupled receptor (GPCR) signaling to disorders involving the nervous system, Dohlman drew our attention to a study that used a computational approach to build a better opioid (Fig. Although the use of opioids to relieve pain dates back thousands of years, their pain-relieving properties are counterbalanced by serious side effects, such as addiction and potentially fatal respiratory depression, and their abuse has become a serious global problem () used the recently reported crystal structure of the μ-opioid receptor to computationally dock more than 3 million compounds to the ligand-binding pocket, in the hopes of identifying compounds that engaged the receptor in new ways to stabilize unique conformations. The authors then used structure-based optimization to synthesize PZM21, a compound that displayed Gα-biased signaling and, remarkably, potently elicited long-lasting relief from pain in mice. The ) describing the development of a substrate-derived GSK-3 inhibitor with a unique mechanism of action (Fig. Unlike other substrate-derived inhibitors, this compound, L807mts, is subject to GSK-3 phosphorylation and binds tightly to the enzyme after undergoing phosphorylation, thereby undergoing conversion from a selective substrate to a potent inhibitor at the catalytic site. L807mts showed promise in a mouse model of Alzheimer’s disease and may herald the development of a new class of kinase inhibitors that are both selective and effective.