Metabolic instability of type 2 deiodinase is transferable to stable proteins independently of subcellular localization

Thyroid hormone activation is catalyzed by two deiodinases, D1 and D2. Whereas D1 is a stable plasma membrane protein, D2 is resident in the endoplasmic reticulum (ER) and has a 20-min half-life due to selective ubiquitination and proteasomal degradation. Here we have shown that stable retention explains D2 residency in the ER, a mechanism that is nevertheless over-ridden by fusion to the long-lived plasma membrane protein, sodium-iodine symporter. Fusion to D2, but not D1, dramatically shortened sodium-iodine symporter half-life through a mechanism dependent on an 18-amino acid D2-specific instability loop. Similarly, the D2-specific loop-mediated protein destabilization was also observed after D2, but not D1, was fused to the stable ER resident protein SEC62. This indicates that the instability loop in D2, but not its subcellular localization, is the key determinant of D2 susceptibility to ubiquitination and rapid turnover rate. Our data also show that the 6 N-terminal amino acids, but not the 12 C-terminal ones, are the ones required for D2 recognition by WSB-1

Endobronchial ultrasound-guided transbronchial needle aspiration for nodal staging in non-small cell lung carcinoma

Introduction: Lung cancer staging has recently evolved to include endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) for nodal assessment. Aim: Evaluate the performance and safety of EBUS-TBNA as a key component of a staging algorithm for non-small cell lung carcinoma (NSCLC) and as a single investigation technique for diagnosis and staging of NSCLC. Methods: Patients undergoing EBUS-TBNA for NSCLC staging at our institution between April 1, 2010 and December 31, 2014 were consecutively included with prospective data collection. EBUS-TBNA was performed under general anesthesia through a rigid scope. Results: A total of 122 patients, 84.4% males, mean age 64.2 years. Histological type: 78 (63.9%) adenocarcinoma, 33 (27.0%) squamous cell carcinoma, 11 (8.9%) undifferentiated/other NSCLC. A total of 435 lymph node stations were punctured. Median number of nodes per patient was 4. EBUS-TBNA nodal staging: 63 (51.6%) N0; 8 (6.5%) N1; 34 (27.9%) N2, and 17 (13.9%) N3. EBUS-TBNA was the primary diagnostic procedure in 27 (22.1%) patients. EBUS-TBNA NSCLC staging had a sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy rate of 83.3, 100, 100, 86.1, and 91.8%, respectively. No complications were attributable to the procedure. Conclusion: A comprehensive lung cancer staging strategy that includes EBUS-TBNA seems to be safe and effective. Our EBUS-TBNA performance and safety in this particular setting was in line with previously published reports. Additionally, our study showed that, in selected patients, lung cancer diagnosis and staging are achievable with a single endoscopic technique. Keywords: EBUS-TBNA, Non-small cell lung carcinoma, Nodal stagin

Ubiquitination-Induced Conformational Change within the Deiodinase Dimer Is a Switch Regulating Enzyme Activity▿

Ubiquitination is a critical posttranslational regulator of protein stability and/or subcellular localization. Here we show that ubiquitination can also regulate proteins by transiently inactivating enzymatic function through conformational change in a dimeric enzyme, which can be reversed upon deubiquitination. Our model system is the thyroid hormone-activating type 2 deiodinase (D2), an endoplasmic reticulum-resident type 1 integral membrane enzyme. D2 exists as a homodimer maintained by interacting surfaces at its transmembrane and globular cytosolic domains. The D2 dimer associates with the Hedgehog-inducible ubiquitin ligase WSB-1, the ubiquitin conjugase UBC-7, and VDU-1, a D2-specific deubiquitinase. Upon binding of T4, its natural substrate, D2 is ubiquitinated, which inactivates the enzyme by interfering with D2's globular interacting surfaces that are critical for dimerization and catalytic activity. This state of transient inactivity and change in dimer conformation persists until deubiquitination. The continuous association of D2 with this regulatory protein complex supports rapid cycles of deiodination, conjugation to ubiquitin, and enzyme reactivation by deubiquitination, allowing tight control of thyroid hormone action