Cch1p mediates Ca2+ influx to protect Saccharomyces cerevisiae against eugenol toxicity

Eugenol has antifungal activity and is recognised as having therapeutic potential. However, little is known of the cellular basis of its antifungal activity and a better understanding of eugenol tolerance should lead to better exploitation of eugenol in antifungal therapies. The model yeast, Saccharomyces cerevisiae, expressing apoaequorin was used to show that eugenol induces cytosolic Ca2+ elevations. We investigated the eugenol Ca2+ signature in further detail and show that exponentially growing cells exhibit Ca2+ elevation resulting exclusively from the influx of Ca2+ across the plasma membrane whereas in stationary growth phase cells Ca2+ influx from intracellular and extracellular sources contribute to the eugenol-induced Ca2+ elevation. Ca2+ channel deletion yeast mutants were used to identify the pathways mediating Ca2+ influx; intracellular Ca2+ release was mediated by the vacuolar Ca2+ channel, Yvc1p whereas the Ca2+ influx across the plasma membrane could be resolved into Cch1p-dependent and Cch1p-independent pathways. We show that the growth of yeast devoid the plasma membrane Ca2+ channel, Cch1p, was hypersensitive to eugenol and that this correlated with reduced Ca2+ elevations. Taken together, these results indicate that a cch1p-mediated Ca2+ influx is part of an intracellular signal which protects against eugenol toxicity. This study provides fresh insight into the mechanisms employed by fungi to tolerate eugenol toxicity which should lead to better exploitation of eugenol in antifungal therapies

Do compensation plans with performance targets provide better incentives?

YesGuided by academic literature, industry practice and policy recommendations, we analyze a wide range of option and restricted stock plans with exercise and vesting conditions that may be contingent on stock price performance. To assess the effectiveness of these plans at attracting and providing incentives to executives, we create compensation plans with fixed firm cost and executive valuation and calculate their expected total lifetime incentives. We show that performance vesting targets provide the least cost effective incentives, performance exercise targets provide the largest risk incentives, option plans are generally superior to restricted stock plans, and calendar vesting is only efficient up to a maximum of three years. Performance exercise targets can increase the expected total lifetime incentives provided by compensation plans, but in general, standard options with short vesting periods provide the most cost effective pay-for-performance incentives

Why do employees like to be paid with Options?: A multi-period prospect theory approach

The use of options as compensation for non-executive employees is a puzzle. Standard, rational, valuation models show that the cost of issuing options is larger than the value placed on the options by employees. Existing explanations for this puzzle are based upon static models that ignore the considerable dynamic aspects of employee stock option pricing and exercise behavior. We develop dynamic, multiperiod models of employee preferences considering risk aversion, loss aversion, overconfidence and probability weighting to test possible explanations of the use of employee stock options. We find that a cumulative prospect theory model generates scenarios where employees would prefer options to either cash or equity payments, and also optimally exercise their options early. This is the only model where options are preferred and also optimally exercised early. (C) 2016 Elsevier B.V. All rights [email protected]; [email protected]