Revealing CD38 cellular localization using a cell permeable, mechanism-based fluorescent small-molecule probe.

Nicotinamide adenine dinucleotide (NAD) is increasingly recognized as an important signaling molecule that affects numerous biological pathways. Thus, enzymes that metabolize NAD can have important biological functions. One NAD-metabolizing enzyme in mammals is CD38, a type II transmembrane protein that converts NAD primarily to adenosine diphosphate ribose (ADPR) and a small amount of cyclic adenosine diphosphate ribose (cADPR). Localization of CD38 was originally thought to be only on the plasma membrane, but later reports showed either significant or solely, intracellular CD38. With the efficient NAD-hydrolysis activity, the intracellular CD38 may lead to depletion of cellular NAD, thus producing harmful effects. Therefore, the intracellular localization of CD38 needs to be carefully validated. Here, we report the synthesis and application of a cell permeable, fluorescent small molecule (SR101-F-araNMN) that can covalently label enzymatically active CD38 with minimal perturbation of live cells. Using this fluorescent probe, we revealed that CD38 is predominately on the plasma membrane of Raji and retinoic acid (RA)-treated HL-60 cells. Additionally, the probe revealed no CD38 expression in K562 cells, which was previously reported to have solely intracellular CD38. The finding that very little intracellular CD38 exists in these cell lines suggests that the major enzymatic function of CD38 is to hydrolyze extracellular rather than intracellular NAD. The fluorescent activity-based probes that we developed allow the localization of CD38 in different cells to be determined, thus enabling a better understanding of the physiological function.

Severe epistaxis after posterior nasal nerve ablation requiring surgical intervention: A multi-center case series.

KEY POINTS: Severe epistaxis occurs in 2% of PNN ablation cases, independent of method or device type. Major epistaxis requiring intervention after PNN ablation can occur on average 20 days post-procedure.

Pediatric head and neck trauma from all-terrain vehicle accidents.

OBJECTIVE: To characterize pediatric head and neck trauma from all-terrain vehicles (ATVs) at a single institution. STUDY DESIGN/SETTING: Retrospective case series at a level I pediatric trauma center. RESULTS: Thirty-four patients were admitted: average age was 12 years, with 68% between 12 and 16 years and 32% under 12 years. The patient was the driver in 74% of cases and the passenger in 17% of cases. Driver average age was 12.7 years and passenger average age was 10.5 years. Seventy-six percent of children were not wearing helmets. Average hospital stay was 6 days, with 81% of cases discharged home. Central nervous system injuries were most common, followed by soft tissue injuries. Soft tissue repair was the most frequent procedure, and most maxillofacial fractures required operative intervention. CONCLUSIONS: ATV-related morbidity and mortality in children are significant public health issues amenable to primary prevention by prohibiting passengers on ATVs and requiring helmet use. SIGNIFICANCE: National trends indicate increasing ATV-related injuries in children.