The therapeutic value of DNA-damaging antineoplastic agents is dependent upon their ability to induce tumor cell apoptosis while sparing most normal tissues. Here, we show that a component of the apoptotic response to these agents in several different types of tumor cells is the deamidation of two asparagines in the unstructured loop of Bcl-xL, and we demonstrate that deamidation of these asparagines imports susceptibility to apoptosis by disrupting the ability of Bcl-xL to block the proapoptotic activity of BH3 domain-only proteins. Conversely, Bcl-xL deamidation is actively suppressed in fibroblasts, and suppression of deamidation is an essential component of their resistance to DNA damage-induced apoptosis. Our results suggest that the regulation of Bcl-xL deamidation has a critical role in the tumor-specific activity of DNA-damaging antineoplastic agents.

In Deverman et al. (Cell 111, 51-62), we concluded that deamidation inactivates Bcl-x L . This conclusion was based partly on results obtained using Bcl-x L constructs in which asparagines 52 and 66 were replaced with aspartates to mimic deamidation. We reported that these constructs lacked the antiapoptotic and BIM-binding function of native Bcl-x L (Figure 4). However, during the course of subsequent studies, we discovered a previously undetected mutation in these constructs. When this secondary mutation was corrected and the resulting constructs were assessed as in Figure 4, we found that their antiapoptotic activity was similar to that of wild-type Bcl-x L and their BIMbinding activity was restored. However, we stand by our conclusion that deamidation results in the loss of cellular Bcl-x L activity. This is evidenced by our finding that replacement of asparagines 52 and 66 in Bcl-x L with alanines [Bcl-x L (N52A/N66A)] to block deamidation increases the antiapoptotic activity of Bcl-x L , which is stated as "data not shown" in our manuscript (second paragraph from the bottom of the righthand column on page 55). Thus, all of the other conclusions in the manuscript remain supported. We are currently pursuing studies to determine the precise mechanism by which deamidation results in the loss of cellular Bcl-x L activity.We sincerely apologize for the confusion we have caused.

PURPOSE Urinary tract obstruction causes hydroureteronephrosis and requires surgical intervention to prevent the development of permanent renal injury. While many studies have focused on the development of renal injuries, here we examine the molecular mechanisms that promote renal recovery following the correction of obstruction. MATERIALS AND METHODS A reversible murine model of ureteral obstruction was used to examine the BMP-7 and TGF-β signaling pathways during renal recovery following obstruction-induced injury. Analysis was conducted using standard molecular techniques including RT-PCR, ELISA, immunoblotting, and co-immunoprecipitation. RESULTS We found that the upregulation of BMP-7 following the correction of obstruction inhibits TGF-β-dependent pro-fibrotic pathways that are central to the pathogenesis of renal injury. The inhibitory effects of BMP-7 are mediated, in part, by the activation of its downstream target proteins, Smad1, Smad5, and Smad8, which suppress the activity of TGF-β-dependent Smad proteins and, in turn, inhibit the expression of TGF-β-dependent genes. Finally, the activation of the BMP-7–Smad1/5/8 pathway during renal recovery promotes the restoration of renal architecture and resolution of fibrosis in the kidney following the correction of obstruction. CONCLUSIONS Together, these findings demonstrate that the BMP-7–Smad1/5/8 pathway promotes the repair of the kidney following obstruction-induced injury. Accordingly, the BMP-7 pathway represents an important therapeutic target to stimulate the innate repair mechanisms of the kidney during the treatment of obstruction-induced renal injuries.

Manson SR, Niederhoff RA, Hruska KA, Austin PF. Endogenous BMP-7 is a critical molecular determinant of the reversibility of obstruction-induced renal injuries.

The proliferation of all nontransformed adherent cells is dependent upon the development of mechanical tension within the cell; however, little is known about the mechanisms by which signals regulated by mechanical tension are integrated with those regulated by growth factors. We show here that Skp2, a component of a ubiquitin ligase complex that mediates the degradation of several proteins that inhibit proliferation, is upregulated when increased mechanical tension develops in intact smooth muscle and that its upregulation is critical for the smooth muscle proliferative response to increased mechanical tension. Notably, whereas growth factors regulate Skp2 at the level of protein stability, we found that mechanical tension regulates Skp2 at the transcriptional level. Importantly, we demonstrate that the calcium-regulated transcription factor NFATc1 is a critical mediator of the effect of increased mechanical tension on Skp2 transcription. These findings identify Skp2 as a node at which signals from mechanical tension and growth factors are integrated to regulate proliferation, and they define calcium-NFAT-Skp2 signaling as a critical pathway in the mechanoregulation of proliferation.Cellular proliferation is regulated by (i) soluble factors, (ii) adhesion to the extracellular matrix, and (iii) the mechanical tension within the cytoskeleton. Although most studies of the regulation of proliferation have focused on the role of soluble factors and adhesion, it is clear that the role of the mechanical tension within the cytoskeleton is of equal importance. In fact, the proliferation of all nontransformed adherent cells is dependent upon the development of mechanical tension (21).The level of mechanical tension within the cytoskeleton is determined by three factors: (i) the tractional force generated by the cytoskeleton, (ii) the compliance of the extracellular matrix, and (iii) any pulling force transmitted through the extracellular matrix to the cell. These three factors are likely to have a critical regulatory role in every nonhematologic process in which proliferation occurs. Indeed, it has been noted that the sharp differences in the tissue patterns that arise across distances of less than a micrometer during organogenesis, tissue remodeling, and tissue repair cannot be attributed solely to gradients of soluble growth factors. Instead, it has been proposed that it is the differential regulation of proliferation by localized differences in mechanical tension that in large part sculpts the micromorphology of developing, remodeling, and repairing tissues (21). Although many of the "upstream" components of the signal transduction pathways that serve to mediate the mechanoregulation of proliferation, such as integrins, focal adhesion kinase, and the small GTPases RhoA and Rac, have been characterized (2), there is little known about those components that serve to couple mechanical signaling directly to the central cell cycle regulatory machinery.To begin to identify such "downstream" components of the signal transduc...