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Ribosomal S6 kinase 2 (S6K2) acts downstream of the mammalian target of rapamycin (mTOR). Here, we show that some S6K2 localize at the centrosome throughout the cell cycle. S6K2 is found in the pericentriolar area of the centrosome. S6K2 centrosomal localization is unaffected by serum withdrawal or treatment with rapamycin, wortmannin, U0126, or phorbol-12-myristate-13-acetate (PMA). Unlike S6K2, S6 kinase 1 (S6K1) does not localize at the centrosome, suggesting the two kinases may also have nonoverlapping functions. Our data suggest that centrosomal S6K2 may have a role in the phosphoinositide-3-kinase (PI3K)/Akt/mTOR signaling pathway that has also been detected in the centrosome.

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Introduction The coronavirus 2019 pandemic caused a shortage of disposable N95 respirators, prompting healthcare entities to extend the use of these masks beyond their intended single-use manufacturer recommendation with a paucity of supporting research. Methods We performed a prospective cohort study of ED healthcare workers (HCW) (“subjects”) required to use respirators at an academic, Level I trauma center. Subjects had been previously fit tested and assigned an appropriately sized N95 mask per hospital protocol. Per study protocol, subjects were fit tested periodically throughout their shifts and on multiple shifts over the eight-week study period. Data points collected included the age of the mask, subjective assessment of mask seal quality, and fit test results. We analyzed the data using Fisher’s exact test, and calculated odds ratios (OR) to determine the failure rate of disposable N95 masks following reuse. Results A total of 130 HCWs underwent fit testing and 127 were included for analysis. Mask failure rate climbed after day 2 of use, with 33.3% of masks failing at day 3, 42.9% at day 4, and 50% at ≥ day 5. Categorizing the masks into those being used for two or fewer days vs those in use for three or more, failure was more common on day 3 of use or older compared to those in the first two days of use (41.8% vs 8.3%, P < 0.0001) with an OR of failure with an older mask of 7.9 (confidence interval [CI], 2.8–22.3). The healthcare workers’ assessment of poor seal was 33.3% sensitive (CI, 18.6–51.9) and 95.7% specific (CI, 88.8–98.6) for fit test failure. Conclusion Disposable N95 masks have significant failure rates following reuse in clinical practice. Healthcare personnel also performed poorly in assessing the integrity of the seal of their disposable respirators.

During the SARS-CoV-2 pandemic, many emergency departments (EDs) initiated continuous use of N95 disposable respirators (N95s) rather than discarding them after each use to conserve respirators. This study investigates the efficacy of wearing disposable N95s continuously during clinical work. Methods This is a prospective cohort study of ED staff required to wear N95s continuously throughout their shifts. Subjects were doctors, nurses, and technicians who were previously fitted for their assigned N95 by employee health. Subjects were fit tested periodically throughout their shifts. Investigators filled out a questionnaire for each subject noting the hours of continuous N95 wear. Data were analyzed using descriptive statistics. Results One hundred thirteen N95s were evaluated, with 23 failures at first testing. These were not retested. Twenty-seven N95s passed at the start of a shift and did not have repeat testing during the course of the shift. These were excluded from further analysis. Seventeen N95s passed testing after several hours of continuous wear, but only had a single fit test done partway or at the end of a shift. These were assumed to have passed if tested at shift start, and were assigned as “passes” for continuous use. Forty-six N95s had an initial pass and were evaluated for continuous use, of which 6 subsequently failed later in the shift, giving a fail rate with continuous use of 9.5%. Conclusion Continuous use of disposable N95s throughout an ED shift is reasonable during a PPE shortage if wearers are assured of fit at the start of their shift.