The interleukin-1 beta (IL-1 beta) converting enzyme (ICE) processes the inactive IL-1 beta precursor to the proinflammatory cytokine. Adherent monocytes from mice harboring a disrupted ICE gene (ICE-/-) did not export IL-1 beta or interleukin-1 alpha (IL-1 alpha) after stimulation with lipopolysaccharide. Export of tumor necrosis factor-alpha and interleukin-6 (IL-6) from these cells was also diminished. Thymocytes from ICE-/- mice were sensitive to apoptosis induced by dexamethasone or ionizing radiation, but were resistant to apoptosis induced by Fas antibody. Despite this defect in apoptosis, ICE-/- mice proceed normally through development.

FLT3 is a type III receptor tyrosine kinase that is thought to play a key role in hematopoiesis. Certain classes of FLT3 mutations cause constitutively activated forms of the receptor that are found in significant numbers of patients with acute myelogenous leukemia (AML). The mutations occur either in the activation loop, for example, as point mutations of Asp835 or as internal tandem duplication (ITD) sequences in the juxtamembrane (JM) domain. To further understand the nature of FLT3 autoinhibition and regulation, we have determined the crystal structure of the autoinhibited form of FLT3. This structure shows the autoinhibitory conformation of a complete JM domain in this class of receptor tyrosine kinases. The detailed inhibitory mechanism of the JM domain is revealed, which is likely utilized by other members of type III receptor tyrosine kinases.

Dysregulation of the calcitonin gene-related peptide (CGRP), a potent vasodilator, is directly implicated in the pathogenesis of migraine. CGRP binds to and signals through the CGRP receptor (CGRP-R), a heterodimer containing the calcitonin receptor-like receptor (CLR), a class B GPCR, and RAMP1, a receptor activity-modifying protein. We have solved the crystal structure of the CLR/RAMP1 N-terminal ectodomain heterodimer, revealing how RAMPs bind to and potentially modulate the activities of the CLR GPCR subfamily. We also report the structures of CLR/RAMP1 in complex with the clinical receptor antagonists olcegepant (BIBN4096BS) and telcagepant (MK0974). Both drugs act by blocking access to the peptide-binding cleft at the interface of CLR and RAMP1. These structures illustrate, for the first time, how small molecules bind to and modulate the activity of a class B GPCR, and highlight the challenges of designing potent receptor antagonists for the treatment of migraine and other class B GPCR-related diseases.

We have identified a novel cDNA encoding a protein (named TX) with > 50% overall sequence identity with the interleukin‐1 beta converting enzyme (ICE) and approximately 30% sequence identity with the ICE homologs NEDD‐2/ICH‐1L and CED‐3. A computer homology model of TX was constructed based on the X‐ray coordinates of the ICE crystal recently published. This model suggests that TX is a cysteine protease, with the P1 aspartic acid substrate specificity retained. Transfection experiments demonstrate that TX is a protease which is able to cleave itself and the p30 ICE precursor, but not to generate mature IL‐1 beta from pro‐IL‐1 beta. In addition, this protein induces apoptosis in transfected COS cells. TX therefore delineates a new member of the growing Ice/ced‐3 gene family coding for proteases with cytokine processing activity or involved in programmed cell death.

BiochemistryExpression and characterization of human FKBP52, an immunophilin that associates with the 90-kDa heat shock protein and is a component of steroid receptor complexes Communicated by Etienne-Emile Baulieu, August 17, 1992 ABSTRACT Using an FK506 affinity column to identify mammalian immunosuppressant-binding proteins, we identified an immunophilin with an apparent Mr 55,000, which we have named FKBP52. We used chemically determined peptide sequence and a computerized algorithm to search GenPept, the translated GenBank data base, and identified two cDNAs likely to encode the murine FKBP52 homolog. We amlifed a murine cDNA fragment, used it to select a human FKBP52 (hFKBP52) cDNA clone, and then used the done to deduce the hFKBP52 sequence (calculated Mr 51,810) and to express hFKBP52 in Escherichia coi. Recombinant hFKBP52 has peptidyl-prolyl cis-trans isomerase activity that is inhibited by FK506 and rapamycin and an FKBP12-like consensus sequence that probably defines the immunosuppressant-binding site. FKBP52 Is apparently common to several vertebrate species and associates with the 90-kDa heat shock protein (hsp90) in untransformed mammalian steroid receptor complexes. The putative immunosuppressant-binding site is probably distinct from the hsp90-binding site, and we predict that FKBP52 has different structural domains to accommodate these functions. hFKBP52 contains 12 protein kinase phosphorylation-site motifs MATERIALS AND METHODSPreparation of an FK506 Affinity Matrix and Isolation of FKBPs. An amino derivative of FK506 was prepared (10) and coupled to Affi-Gel 10 (Bio-Rad) in methanol overnight; unreacted groups were blocked with 50 mM ethanolamine. FKBPs from calf thymus cytosol were prepared by using the matrix as described (11), dialyzed at 40C against 10 mM Tris-HCl (pH 7.0), lyophilized, reconstituted in SDS sample buffer, and resolved in a 12.5% acrylamide gel. Proteins were stained (Fig. 1A) or electroblotted.Protein Sequence Determination of bFKBP52. The Mr 55,000 band, later called bFKBP52, was stained on and excised from Immobilon-P (Millipore) for automated aminoterminal sequencing (26). Peptides were generated with endoproteinase Lys-C (Wako Chemicals USA, Richmond, VA) and separated by microbore C18 HPLC and eluted at 200A.l/min from 5% B at 0 min to 33% B at 65 min, 60%6 B at 90 min, and 100% B at 105 min (solvent A, 0.09%o trifluoroacetic acid in water; solvent B, 0.06% trifluoroacetic acid in acetonitrile). Effluent fractions corresponding to absorption peaks at 214 nm were collected, stored immediately at -200C, and applied later to a Polybrene-precycled glass-fiber filter for sequencing.Isolation of a Human cDNA Encoding FKBP52. Using BLAST (27) to search GenPept (translated GenBank Release 64.3 with daily updates, searched on July 11, 1991) with the deduced hFKBP12 sequence (7, 8), we identified two related murine polypeptides (encoded by GenBank sequences X17068 and X17069) that shared significant sequence identity with our bFKBP52 sequence (Fig. 2). Two DNA oligomers...