with HKL 24 or XDS 25 . Crystals belong to space group P2 1 2 1 2 1 with unit cell dimensions a ¼ 56.7 Å , b ¼ 67.7 Å and c ¼ 135.6 Å , and contain three molecules per asymmetric unit. Structure determinationSelenium sites were located with SnB 26 . MAD phases were calculated with SHARP 27 and improved by density modification. A CID model was built with O 28 and refined with CNS 29 . The refined model has excellent stereochemical quality and a free R-factor of 25.2%. A difference Fourier for the peptide-soaked crystal was calculated with phases from the CID model and identified strong density for the CTD peptide bound to one CID molecule (chain B). The two other CID molecules pack against each other, burying their peptide-binding sites. After peptide building, the CID-CTD model was refined to a free R-factor of 25.7%. Peptide binding does not result in significant conformational changes in the CID domain. Soaking experiments with phosphoserine did not reveal any additional electron density. D 54, 799-804 (1998). 27. Terwilliger, T. C. Automated structure solution, density modification and model building. Acta. Crystallogr. 58, 1937Crystallogr. 58, -1940Crystallogr. 58, (2002 Competing interests statement The authors declare that they have no competing financial interests.Correspondence and requests for materials should be addressed to P.C.(cramer@lmb.uni-muenchen.de). Atomic coordinates and structure factors for the Pcf11 CID domain and the CTD-CID complex have been deposited in the Protein Data Bank under accession numbers 1SZ9 and 1SZA, respectively.

SUMMARY Several lines of evidence suggest that mitochondrial dysfunction plays a critical role in the pathogenesis of microvascular complications of diabetes, including diabetic nephropathy. However, the signaling pathways by which hyperglycemia leads to mitochondrial dysfunction are not fully understood. Here we examined the role of Rho-associated coiled-coil containing protein kinase 1 (ROCK1) on mitochondrial dynamics by generating two diabetic mouse models with targeted deletions of ROCK1, and an inducible podocyte-specific knock-in mouse expressing a constitutively active (cA) mutant of ROCK1. Our findings suggest that ROCK1 mediates hyperglycemia-induced mitochondrial fission by promoting dynamin-related protein-1 (Drp1) recruitment to the mitochondria. Deletion of ROCK1 in diabetic mice prevented mitochondrial fission, whereas podocyte-specific cA-ROCK1 mice exhibited increased mitochondrial fission. Importantly, we found that ROCK1 triggers mitochondrial fission by phosphorylating Drp1 at Serine 600 residue. These findings provide insights into the unexpected role of ROCK1 in a signaling cascade that regulates mitochondrial dynamics.

TGFbeta signaling controls diverse normal developmental processes and pathogenesis of diseases including cancer and autoimmune and fibrotic diseases. TGFbeta responses are generally mediated through transcriptional functions of Smads. A key step in TGFbeta signaling is ligand-induced phosphorylation of receptor-activated Smads (R-Smads) catalyzed by the TGFbeta type I receptor kinase. However, the potential of Smad dephosphorylation as a regulatory mechanism of TGFbeta signaling and the identity of Smad-specific phosphatases remain elusive. Using a functional genomic approach, we have identified PPM1A/PP2Calpha as a bona fide Smad phosphatase. PPM1A dephosphorylates and promotes nuclear export of TGFbeta-activated Smad2/3. Ectopic expression of PPM1A abolishes TGFbeta-induced antiproliferative and transcriptional responses, whereas depletion of PPM1A enhances TGFbeta signaling in mammalian cells. Smad-antagonizing activity of PPM1A is also observed during Nodal-dependent early embryogenesis in zebrafish. This work demonstrates that PPM1A/PP2Calpha, through dephosphorylation of Smad2/3, plays a critical role in terminating TGFbeta signaling.

and collect data. BHC helped generate Tug1-transgenic mice and edit the manuscript. PAO helped edit the manuscript, and FRD oversaw experiments, prepared the manuscript, and provided guidance on overall project design.