Faculty Bibliography

Axon degeneration, a hallmark of chemotherapy-induced peripheral neuropathy (CIPN), is thought to be caused by a loss of the essential metabolite nicotinamide adenine dinucleotide (NAD⁺) via the prodegenerative protein SARM1. Some studies challenge this notion, however, and suggest that an aberrant increase in a direct precursor of NAD⁺, nicotinamide mononucleotide (NMN), rather than loss of NAD⁺, is responsible. In support of this idea, blocking NMN accumulation in neurons by expressing a bacterial NMN deamidase protected axons from degeneration. We hypothesized that protection could similarly be achieved by reducing NMN production pharmacologically. To achieve this, we took advantage of an alternative pathway for NAD⁺ generation that goes through the intermediate nicotinic acid mononucleotide (NAMN), rather than NMN. We discovered that nicotinic acid riboside (NAR), a precursor of NAMN, administered in combination with FK866, an inhibitor of the enzyme nicotinamide phosphoribosyltransferase that produces NMN, protected dorsal root ganglion (DRG) axons against vincristine-induced degeneration as well as NMN deamidase. Introducing a different bacterial enzyme that converts NAMN to NMN reversed this protection. Collectively, our data indicate that maintaining NAD⁺ is not sufficient to protect DRG neurons from vincristine-induced axon degeneration, and elevating NMN, by itself, is not sufficient to cause degeneration. Nonetheless, the combination of FK866 and NAR, which bypasses NMN formation, may provide a therapeutic strategy for neuroprotection.

Nicotinamide adenine dinucleotide (NAD(+)) is an essential substrate for sirtuins and poly(adenosine diphosphate-ribose) polymerases (PARPs), which are NAD(+)-consuming enzymes localized in the nucleus, cytosol, and mitochondria. Fluctuations in NAD(+) concentrations within these subcellular compartments are thought to regulate the activity of NAD(+)-consuming enzymes; however, the challenge in measuring compartmentalized NAD(+) in cells has precluded direct evidence for this type of regulation. We describe the development of a genetically encoded fluorescent biosensor for directly monitoring free NAD(+) concentrations in subcellular compartments. We found that the concentrations of free NAD(+) in the nucleus, cytoplasm, and mitochondria approximate the Michaelis constants for sirtuins and PARPs in their respective compartments. Systematic depletion of enzymes that catalyze the final step of NAD(+) biosynthesis revealed cell-specific mechanisms for maintaining mitochondrial NAD(+) concentrations.

Translation regulation is a fundamental component of gene expression, allowing cells to respond rapidly to a variety of stimuli in the absence of new transcription. The lack of methods for profiling nascent proteomes in distinct cell populations in heterogeneous tissues has precluded an understanding of translational regulation in physiologically relevant contexts. Here, we describe a chemical genetic method that involves orthogonal enzyme-mediated incorporation of a clickable puromycin analogue into nascent polypeptides. Using this method, we show that we can label newly synthesized proteins in a cell-specific manner in cells grown in culture and in heterogeneous tissues. We also show that we can identify the nascent proteome in genetically targeted cell populations using affinity enrichment and tandem mass spectrometry. Our method has the potential to provide unprecedented insights into cell-specific translational regulation in heterogeneous tissues.

BACKGROUND: BRAF mutations activate the mitogen-activated protein kinase pathway and often confer an aggressive thyroid cancer (TC) phenotype. Spry2 is an inducible negative feedback regulator of the mitogen-activated protein kinase (MAPK) pathway. The aim of this study was to investigate the role of Spry2 in TC. METHODS: TC cell lines were analyzed for Spry2 expression and MAPK pathway activation. Cells were treated with MEK inhibitor and Spry2 small hairpin RNA. Cells were analyzed for Spry2 expression and MEK/ERK phosphorylation (pMEK, pERK). Thirty human papillary TCs were analyzed for mitogen-activated protein kinase pathway activating mutations and Spry2 expression. RESULTS: Increased baseline pMEK levels and Spry2 expression was found in BRAF V600E mutant (BRAF+) cells. MEK inhibition in BRAF+ cells showed decreased Spry2 expression and decreased pMEK/pERK levels. From our tissue samples, 10 papillary TCs had BRAF mutation, and increased Spry2 expression was found only in BRAF+ tumors. CONCLUSION: Spry2 expression correlates with BRAF status in vitro and in human tissue. Spry2 may serve as a negative feedback regulator of the mitogen-activated protein kinase pathway in BRAF+ TC. Increased Spry2 expression may serve as a surrogate marker of mitogen-activated protein kinase pathway activation with prognostic and therapeutic implications

The BimEL tumor suppressor is a potent proapoptotic BH3-only protein. We found that, in response to survival signals, BimEL was rapidly phosphorylated on three serine residues in a conserved degron, facilitating binding and degradation via the F box protein betaTrCP. Phosphorylation of the BimEL degron was executed by Rsk1/2 and promoted by the Erk1/2-mediated phosphorylation of BimEL on Ser69. Compared to wild-type BimEL, a BimEL phosphorylation mutant unable to bind betaTrCP was stabilized and consequently potent at inducing apoptosis by the intrinsic mitochondrial pathway. Moreover, although non-small cell lung cancer (NSCLC) cells often become resistant to gefitinib (a clinically relevant tyrosine kinase inhibitor that induces apoptosis through BimEL), silencing of either betaTrCP or Rsk1/2 resulted in BimEL-mediated apoptosis of both gefitinib-sensitive and gefitinib-insensitive NSCLC cells. Our findings reveal that betaTrCP promotes cell survival in cooperation with the ERK-RSK pathway by targeting BimEL for degradation

PURPOSE: We evaluated the efficacy of a combined chemoradiation therapy protocol for the primary treatment of primary invasive carcinoma of the male urethra. MATERIALS AND METHODS: From January 1991 to December 2006, 18 patients with invasive carcinoma of the male urethra referred to our institution were treated with a chemoradiation therapy protocol, consisting of 2 cycles of 5-fluorouracil (1,000 mg/m(2)) on days 1 to 4 and days 29 to 32, and mitomycin-C (10 mg/m(2)) on days 1 and 29 with concurrent external beam radiation therapy (45 to 55 Gy in 25 fractions during 5 weeks) to the genitalia, perineum, and inguinal and external iliac lymph nodes. Kaplan-Meier curves were constructed to assess overall, disease specific and disease-free survival. RESULTS: The stage and node distribution was T2N0 in 2 patients (11%), T3N0 in 8 (44%), T4N0 in 2 (11%), TXN1 in 1(6%) and TXN2 in 5 (28%). The most prevalent histology was moderately (7 of 18 patients or 39%) or poorly (10 of 18 or 56%) differentiated squamous cell carcinoma (17 of 18 or 95%). Overall 83% (15 of 18) of the patients had a complete response to the primary chemoradiation therapy protocol, and the 5-year overall and disease specific survival rates were 60% and 83%, respectively. Five-year disease-free survival rates after chemoradiation therapy and after chemoradiation therapy with salvage surgery were 54% and 72%, respectively. The 3 nonresponders died of disease after undergoing salvage surgery and 5 of the 15 complete responders (30%) had recurrence. Complex urethral reconstruction was required in 3 of 10 patients (30%) who had prolonged disease-free survival. CONCLUSIONS: The chemoradiation therapy protocol is an alternative primary treatment modality for invasive urethral carcinoma. It enables an unprecedented potential for organ preservation

CONTEXT: Children exposed to a traumatic event may be at higher risk for developing mental disorders. The prevalence of child psychopathology, however, has not been assessed in a population-based sample exposed to different levels of mass trauma or across a range of disorders. OBJECTIVE: To determine prevalence and correlates of probable mental disorders among New York City, NY, public school students 6 months following the September 11, 2001, World Trade Center attack. DESIGN: Survey. SETTING: New York City public schools. PARTICIPANTS: A citywide, random, representative sample of 8236 students in grades 4 through 12, including oversampling in closest proximity to the World Trade Center site (ground zero) and other high-risk areas. MAIN OUTCOME MEASURE: Children were screened for probable mental disorders with the Diagnostic Interview Schedule for Children Predictive Scales. RESULTS: One or more of 6 probable anxiety/depressive disorders were identified in 28.6% of all children. The most prevalent were probable agoraphobia (14.8%), probable separation anxiety (12.3%), and probable posttraumatic stress disorder (10.6%). Higher levels of exposure correspond to higher prevalence for all probable anxiety/depressive disorders. Girls and children in grades 4 and 5 were the most affected. In logistic regression analyses, child's exposure (adjusted odds ratio, 1.62), exposure of a child's family member (adjusted odds ratio, 1.80), and the child's prior trauma (adjusted odds ratio, 2.01) were related to increased likelihood of probable anxiety/depressive disorders. Results were adjusted for different types of exposure, sociodemographic characteristics, and child mental health service use. CONCLUSIONS: A high proportion of New York City public school children had a probable mental disorder 6 months after September 11, 2001. The data suggest that there is a relationship between level of exposure to trauma and likelihood of child anxiety/depressive disorders in the community. The results support the need to apply wide-area epidemiological approaches to mental health assessment after any large-scale disaster

Double gloving has been widely suggested as a means of decreasing exposure to blood and other body fluids. However, most dermatologists do not routinely follow this practice when performing surgical procedures because it reduces manual dexterity and increases costs. To determine whether double gloving should be routinely practiced in dermatologic surgery, pairs of sterile surgical gloves worn during weekly UCLA dermatologic surgery clinics were collected over a period of 3 months and examined for perforations. The procedures gloves were used for ranged from excision of benign lesions, lasting 15 minutes, to hair transplants, lasting 3 hours. Upon completion of the procedures, 8 (5.5%) of 144 pairs of single gloves, 2 (3.7%) of 54 pairs of double inner gloves, and 3 (5.5%) of 54 pairs of double outer gloves were found to have perforations. There were no instances of both the double outer and the double inner gloves having perforations when worn on the same hand. This suggests that double gloving offers a protective advantage by providing extra protection for both the surgeon and the patient during dermatologic surgery