Journal of Biological Chemistry

doi: 10.1016/s0021-9258(20)62965-9pmid: N/A

doi: 10.1016/s0021-9258(20)63032-0pmid: N/A

Weeks, Spencer A.;Lee, Cheri A.;Zhao, Yan;Smidansky, Eric D.;August, Avery;Arnold, Jamie J.;Cameron, Craig E.

doi: 10.1074/jbc.c112.401471pmid: 22854962

<p>Live, attenuated vaccines have prevented morbidity and mortality associated with myriad viral pathogens. Development of live, attenuated vaccines has traditionally relied on empirical methods, such as growth in nonhuman cells. These approaches require substantial time and expense to identify vaccine candidates and to determine their mechanisms of attenuation. With these constraints, at least a decade is required for approval of a live, attenuated vaccine for use in humans. We recently reported the discovery of an active site lysine residue that contributes to the catalytic efficiency of all nucleic acid polymerases (Castro, C., Smidansky, E. D., Arnold, J. J., Maksimchuk, K. R., Moustafa, I., Uchida, A., Götte, M., Konigsberg, W., and Cameron, C. E. (2009) <i>Nat. Struct. Mol. Biol.</i> 16, 212–218). Here we use a model RNA virus and its polymerase to show that mutation of this residue from lysine to arginine produces an attenuated virus that is genetically stable and elicits a protective immune response. Given the conservation of this residue in all viral polymerases, this study suggests that a universal, mechanism-based strategy may exist for viral attenuation and vaccine development.</p>

Vanaman, Thomas;Carafoli, Ernesto

doi: 10.1074/jbc.r112.402354pmid: 22822054

Studies with perfused frog heart in the late 1880s led Sydney Ringer (1) first to identify the essential role of the divalent cation Ca2+ in cardiac muscle contraction. It was a landmark observation that failed to receive the immediate attention it deserved: over the following 60 or 70 years, it was followed only by a handful of scattered findings that confirmed that Ca2+, in addition to its acknowledged structural role in bones and teeth, also has a general role as a carrier of biological signals.

Van Petegem, Filip

doi: 10.1074/jbc.r112.349068pmid: 22822064

<p>Ryanodine receptors (RyRs) are huge ion channels that are responsible for the release of Ca²⁺ from the sarco/endoplasmic reticulum. RyRs form homotetramers with a mushroom-like shape, consisting of a large cytoplasmic head and transmembrane stalk. Ca²⁺ is a major physiological ligand that triggers opening of RyRs, but a plethora of modulatory proteins and small molecules in the cytoplasm and sarco/endoplasmic reticulum lumen have been recognized. Over 300 mutations in RyRs are associated with severe skeletal muscle disorders or triggered cardiac arrhythmias. With the advent of high-resolution structures of individual domains, many of these can be mapped onto the three-dimensional structure.</p>

Lee, Hon Cheung

doi: 10.1074/jbc.r112.349464pmid: 22822066

<p>Cyclic ADP-ribose and nicotinic acid adenine dinucleotide phosphate were discovered >2 decades ago. That they are second messengers for mobilizing Ca²⁺ stores has since been firmly established. Separate stores and distinct Ca²⁺ channels are targeted, with cyclic ADP-ribose acting on the ryanodine receptors in the endoplasmic reticulum, whereas nicotinic acid adenine dinucleotide phosphate mobilizes the endolysosomes via the two-pore channels. Despite the structural and functional differences, both messengers are synthesized by a ubiquitous enzyme, CD38, whose crystal structure and catalytic mechanism have now been well elucidated. How this novel signaling enzyme is regulated remains largely unknown and is the focus of this minireview.</p>

Hilge, Mark

doi: 10.1074/jbc.r112.353573pmid: 22822067

<p>The binding of Ca²⁺ to two adjacent Ca²⁺-binding domains, CBD1 and CBD2, regulates ion transport in the Na⁺/Ca²⁺ exchanger. As sensors for intracellular Ca²⁺, the CBDs form electrostatic switches that induce the conformational changes required to initiate and sustain Na⁺/Ca²⁺ exchange. Depending on the presence of a few key residues in the Ca²⁺-binding sites, zero to four Ca²⁺ ions can bind with affinities between 0.1 to 20 μm. Importantly, variability in CBD2 as a consequence of alternative splicing modulates not only the number and affinities of the Ca²⁺-binding sites in CBD2 but also the Ca²⁺ affinities in CBD1.</p>

Palty, Raz;Hershfinkel, Michal;Sekler, Israel

doi: 10.1074/jbc.r112.355867pmid: 22822063

<p>The mitochondrial membrane potential that powers the generation of ATP also facilitates mitochondrial Ca²⁺ shuttling. This process is fundamental to a wide range of cellular activities, as it regulates ATP production, shapes cytosolic and endoplasmic recticulum Ca²⁺ signaling, and determines cell fate. Mitochondrial Ca²⁺ transport is mediated primarily by two major transporters: a Ca²⁺ uniporter that mediates Ca²⁺ uptake and a Na⁺/Ca²⁺ exchanger that subsequently extrudes mitochondrial Ca²⁺. In this minireview, we focus on the specific role of the mitochondrial Na⁺/Ca²⁺ exchanger and describe its ion exchange mechanism, regulation by ions, and putative partner proteins. We discuss the recent molecular identification of the mitochondrial exchanger and how its activity is linked to physiological and pathophysiological processes.</p>

Racioppi, Luigi;Means, Anthony R.

doi: 10.1074/jbc.r112.356485pmid: 22778263

<p>Many cellular Ca²⁺-dependent signaling cascades utilize calmodulin (CaM) as the intracellular Ca²⁺ receptor. Ca²⁺/CaM binds and activates a plethora of enzymes, including CaM kinases (CaMKs). CaMKK2 is one of the most versatile of the CaMKs and will phosphorylate and activate CaMKI, CaMKIV, and AMP-activated protein kinase. Cell expression of CaMKK2 is limited, yet CaMKK2 is involved in regulating many important physiological and pathophysiological processes, including energy balance, adiposity, glucose homeostasis, hematopoiesis, inflammation, and cancer. Here, we explore known functions of CaMKK2 and discuss its potential as a target for therapeutic intervention.</p>

Monteith, Gregory R.;Davis, Felicity M.;Roberts-Thomson, Sarah J.

doi: 10.1074/jbc.r112.343061pmid: 22822055

<p>Increases in intracellular free Ca²⁺ play a major role in many cellular processes. The deregulation of Ca²⁺ signaling is a feature of a variety of diseases, and modulators of Ca²⁺ signaling are used to treat conditions as diverse as hypertension to pain. The Ca²⁺ signal also plays a role in processes important in cancer, such as proliferation and migration. Many studies in cancer have identified alterations in the expression of proteins involved in the movement of Ca²⁺ across the plasma membrane and subcellular organelles. In some cases, these Ca²⁺ channels or pumps are potential therapeutic targets for specific cancer subtypes or correlate with prognosis.</p>