and the Hoover Institution Partnerships and profit sharing are often claimed to motivate workers by giving them a share of the pie. But in organizations of any significant size, the free-rider effects would seem to choke off any motivational forces. This analysis explores how peer pressure operates and how factors such as profit sharing, shame, guilt, norms, mutual monitoring, and empathy interact to create incentives in the firm. The argument that Japanese firms enjoy team spirit because compensation is linked to overall profitability is analyzed. An explanation for the prevalence of partnerships among individuals in similar occupations is provided. Many firms that use profit-sharing plans claim that such plans have beneficial incentive effects. Partnerships, which share profits, not necessarily equally among partners, are thought by their owners to have some incentive features that are lacking in an employer/employee relationship. Indeed, the idea has even made its way down Madison Avenue into television advertising. Witness, for example, the recent ads for Avis Corporation that boast that the employees are owners and therefore will work harder to serve the customer. But the idea that joint ownership can do much for incentives when the number of workers is large seems wrong on the face of it. After all, each worker We thank Eugene Fama, Peter Mueser, Kevin J. Murphy, and Sherwin Rosen for helpful comments. Financial support was provided by the National Science Foundation.

The serine/threonine kinase Akt/PKB is a major downstream effector of growth factor-mediated cell survival. Activated Akt, like Bcl-2 and Bcl-xL, prevents closure of a PT pore component, the voltage-dependent anion channel (VDAC); intracellular acidification; mitochondrial hyperpolarization; and the decline in oxidative phosphorylation that precedes cytochrome c release. However, unlike Bcl-2 and Bcl-xL, the ability of activated Akt to preserve mitochondrial integrity, and thereby inhibit apoptosis, requires glucose availability and is coupled to its metabolism. Hexokinases are known to bind to VDAC and directly couple intramitochondrial ATP synthesis to glucose metabolism. We provide evidence that such coupling serves as a downstream effector function for Akt. First, Akt increases mitochondria-associated hexokinase activity. Second, the antiapoptotic activity of Akt requires only the first committed step of glucose metabolism catalyzed by hexokinase. Finally, ectopic hexokinase expression mimics the ability of Akt to inhibit cytochrome c release and apoptosis. We therefore propose that Akt increases coupling of glucose metabolism to oxidative phosphorylation and regulates PT pore opening via the promotion of hexokinase-VDAC interaction at the outer mitochondrial membrane. Extrinsic signals emanating from cell-surface growth factor and cytokine receptors are major determinants of mammalian cell survival. The transduction of these signals oppose both basal intrinsic proapoptotic activity, as well as external proapoptotic stimuli (Raff 1992;Raff et al. 1993). Analysis of downstream signaling pathways has shown that activation of the PI-3 kinase/Akt(PKB) pathway plays a major role in cell survival induced by cell surface receptors. Following the initial demonstration that activation of the serine/threonine kinase Akt promotes cell survival (Dudek et al. 1997; KauffmannZeh et al. 1997;Kennedy et al. 1997), mounting reports established Akt as a major determinant of cell survival. Akt has been reported to mediate cell survival by various growth factors and cytokines in a variety of cell types and blocks apoptosis induced by multiple apoptotic stimuli (for review, see Datta et al. 1999;Kandel and Hay 1999). Various specific targets of Akt have been proposed to mediate the antiapoptotic activity of Akt (for review, see Datta et al. 1999;Kandel and Hay 1999). However, because growth factors promote cell survival via maintenance of the metabolic function of mitochondria , it is likely that Akt exerts its effect through similar mechanisms, which may be more fundamental and generally conserved.In mammalian cells, apoptosis has been described as a multistep process that can be initiated by a variety of stimuli. Mitochondria play a major role in this process through the release of cytochrome c and other proapoptotic proteins that normally reside in the intermembrane space between the inner and outer mitochondrial membranes (for review, see Gross et al. 1999;Desagher and Martinou 2000). Cytochrome c release is considered an ea...

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Growth factors signaling through the phosphoinositide 3-kinase/Akt pathway promote cell survival. The mechanism by which the serine/threonine kinase Akt prevents cell death remains unclear. We have previously shown that Akt inhibits the activity of DEVD-targeted caspases without changing the steady-state levels of Bcl-2 and Bcl-x L . Here we show that Akt inhibits apoptosis and the processing of procaspases to their active forms by delaying mitochondrial changes in a caspase-independent manner. Akt activation is sufficient to inhibit the release of cytochrome c from mitochondria and the alterations in the inner mitochondrial membrane potential. However, Akt cannot inhibit apoptosis induced by microinjection of cytochrome c. We also demonstrated that Akt inhibits apoptosis and cytochrome c release induced by several proapoptotic Bcl-2 family members. Taken together, our results show that Akt promotes cell survival by intervening in the apoptosis cascade before cytochrome c release and caspase activation via a mechanism that is distinct from Bad phosphorylation.