AKAP13 couples GPCR signaling to mTORC1 inhibition

The mammalian target of rapamycin complex 1 (mTORC1) senses multiple stimuli to regulate anabolic and catabolic processes. mTORC1 is typically hyperactivated in multiple human diseases such as cancer and type 2 diabetes. Extensive research has focused on signaling pathways that can activate mTORC1 such as growth factors and amino acids. However, less is known about signaling cues that can directly inhibit mTORC1 activity. Here, we identify A-kinase anchoring protein 13 (AKAP13) as an mTORC1 binding protein, and a crucial regulator of mTORC1 inhibition by G-protein coupled receptor (GPCR) signaling. GPCRs paired to Gα_s proteins increase cyclic adenosine 3’5’ monophosphate (cAMP) to activate protein kinase A (PKA). Mechanistically, AKAP13 acts as a scaffold for PKA and mTORC1, where PKA inhibits mTORC1 through the phosphorylation of Raptor on Ser 791. Importantly, AKAP13 mediates mTORC1-induced cell proliferation, cell size, and colony formation. AKAP13 expression correlates with mTORC1 activation and overall lung adenocarcinoma patient survival, as well as lung cancer tumor growth in vivo. Our study identifies AKAP13 as an important player in mTORC1 inhibition by GPCRs, and targeting this pathway may be beneficial for human diseases with hyperactivated mTORC1.     

Conditioning the crab Carcinus maenas against instinctive light avoidance

Carcinus maenas is an invasive species found in Northern American waters overtaking the less adaptable species and responding to various forms of conditioning. In this study, we conditioned C. maenas to reverse its innate light avoidance behavior. Within 6 days of testing, 21 out of 30 crabs were successfully trained to enter a beam of light to receive food, although their instincts are to seek shelter from predators in dark areas. Some took as little as 2 days to reverse their light aversion. They also responded faster once trained. Larger crabs had faster response times than smaller ones, while there was no difference between sexes. The conditioned response lasted for at least 4 days without reinforcement. The rapid learning abilities observed during this experiment may help to explain the pervasive success of C. maenas as an invasive species.     

Prophylactic neuroprotection by blueberry-enriched diet in a rat model of light-induced retinopathy

The role of anthocyanins is controversial in vision health. This study investigates the impact of a blueberry-enriched diet as neuroprotectant in a rat model of light-induced retinopathy. Thirty-eight albino Wistar rats and 25 pigmented Brown–Norway rats were fed by gavage with long (7 weeks) and short (2 weeks) intervention with fortified blueberry juice (1 ml; 2.8 mg cyanidin 3-glucoside equivalents) or with a placebo solution (7 weeks) that contained the abundant nonanthocyanin blueberry phenolic, namely, chlorogenic acid, before being submitted to 2 hours of intense light regimen (1.8×10⁴ lux). Retinal health was measured by fitting electroretinogram responses with the Naka–Rushton equation. The light-induced retinal damage was severe in the placebo groups, with the maximum amplitude of the electroretinogram being significantly reduced in both Wistar and Brown–Norway rats. The maximum amplitude of the electroretinogram was significantly protected from the light insult in the Wistar rats supplemented with blueberry juice for 7 or 2 weeks, and there was no significant difference between these two groups. The same dietary intervention in the Brown–Norway groups failed to protect the retina. Histological examination of retinal section confirmed the electroretinography results, showing protection of the outer nuclear layer of the retina in the Wistar rats fed with blueberries, while all placebo-fed rats and blueberry-fed Brown–Norway rats showed evidence of retinal damage concentrated in the superior hemiretina. The neuroprotective potential of anthocyanins in this particular model is discussed in terms of interaction with rhodopsin/phototransduction and in terms of antioxidative capacity.     

Francisella tularensis inhibits the intrinsic and extrinsic pathways to delay constitutive apoptosis and prolong human neutrophil lifespan

Francisella tularensis is a facultative intracellular bacterium that infects many cell types, including neutrophils. We demonstrated previously that F. tularensis inhibits NADPH oxidase assembly and activity and then escapes the phagosome to the cytosol, but effects on other aspects of neutrophil function are unknown. Neutrophils are short-lived cells that undergo constitutive apoptosis, and phagocytosis typically accelerates this process. We now demonstrate that F. tularensis significantly inhibited neutrophil apoptosis as indicated by morphologic analysis as well as annexin V and TUNEL staining. Thus, ～80% of infected neutrophils remained viable at 48 h compared with ～50% of control cells, and ～40% of neutrophils that ingested opsonized zymosan. In keeping with this finding, processing and activation of procaspases-8, -9, and -3 were markedly diminished and delayed. F. tularensis also significantly impaired apoptosis triggered by Fas crosslinking. Of note, these effects were dose dependent and could be conferred by either intracellular or extracellular live bacteria, but not by formalin-killed organisms or isolated LPS and capsule, and were not affected by disruption of wbtA2 or FTT1236/FTL0708-genes required for LPS O-antigen and capsule biosynthesis. In summary, we demonstrate that F. tularensis profoundly impairs constitutive neutrophil apoptosis via effects on the intrinsic and extrinsic pathways, and thereby define a new aspect of innate immune evasion by this organism. As defects in neutrophil turnover prevent resolution of inflammation, our findings also suggest a mechanism that may in part account for the neutrophil accumulation, granuloma formation, and severe tissue damage that characterizes lethal pneumonic tularemia.     

Low Levels of Nucleotide Diversity in Crocodylus moreletii and Evidence of Hybridization with C. acutus

Examinations of both population genetic structure and the processes that lead to such structure in crocodilians have been initiated in several species in response to a call by the IUCN Crocodile Specialist Group. A recent study used microsatellite markers to characterize Morelet's crocodile (Crocodylus moreletii) populations in north-central Belize and presented evidence for isolation by distance. To further investigate this hypothesis, we sequenced a portion of the mitochondrial control region for representative animals after including samples from additional locales in Belize, Guatemala and Mexico. While there is limited evidence of subdivision involving other locales, we found that most of the differentiation among populations of C. moreletiican be attributed to animals collected from a single locale in Belize, Banana Bank Lagoon. Furthermore, mitochondrial DNA sequence analysis showed that animals from this and certain other locales display a haplotype characteristic of the American crocodile, C. acutus, rather than C. moreletii. We interpret this as evidence of hybridization between the two species and comment on how these new data have influenced our interpretation of previous findings. We also find very low levels of nucleotide diversity in C. moreletiihaplotypes and provide evidence for a low rate of substitution in the crocodilian mitochondrial control region. Finally, the conservation implications of these findings are discussed.     

Primary cutaneous melanoma in Black patients: An analysis of 2464 cases from the National Cancer Database 2004–2018

Melanoma in Black patients carries a poor prognosis. Due to its rarity, melanoma in this population has not been well characterized. This study evaluates survival predictors in Black patients with melanoma. This was a retrospective cohort study of Black patients with cutaneous melanoma from the National Cancer Database 2004–2018. Of the 2464 cases, melanoma was more common among females than males (57.1% vs. 42.9%, p < .001). Median Breslow depth was 1.8 mm (interquartile range 0.4–4.4). Lower extremities were the most common location (52.8%), followed by upper extremities (13.1%) along with otherwise specified/overlapping/other (13.1%), then by trunk (11.8%), and lastly head and neck (9.2%). Stage at diagnosis was I (30.7%), II (27.5%), III (24.1%), and IV (17.7%). Ulceration was observed in 41.4% of lesions. Acral lentiginous melanoma (ALM) was the most common specific histologic subtype (20.3%), followed by superficial spreading melanoma (9.4%). After adjusting for confounders, higher stages and primary site on the head and neck were the strongest independent predictors of worse overall survival. Melanoma in Black patients is most likely to appear on the lower extremities. A large portion (41.8%) presented with stage III or IV disease. ALM was the most common specific histologic subtype.     

Mitofusin 1 and optic atrophy 1 shift metabolism to mitochondrial respiration during aging

Replicative and chronological lifespan are two different modes of cellular aging. Chronological lifespan is defined as the duration during which quiescent normal cells retain their capacity to re‐enter the proliferative cycle. This study investigated whether changes in metabolism occur during aging of quiescent normal human fibroblasts (NHFs) and the mechanisms that regulate these changes. Bioenergetics measurements were taken in quiescent NHFs from younger (newborn, 3‐day, 5‐month, and 1‐year) and older (58‐, 61‐, 63‐, 68‐, and 70‐year) healthy donors as well as NHFs from the same individual at different ages (29, 36, and 46 years). Results show significant changes in cellular metabolism during aging of quiescent NHFs: Old NHFs exhibit a significant decrease in glycolytic flux and lactate levels, and increase in oxygen consumption rate (OCR) and ATP levels compared to young NHFs. Results from the Seahorse XF Cell Mito Stress Test show that old NHFs with a lower Bioenergetic Health Index (BHI) are more prone to oxidative stress compared to young NHFs with a higher BHI. The increase in OCR in old NHFs is associated with a shift in mitochondrial dynamics more toward fusion. Genetic knockdown of mitofusin 1 (MFN1) and optic atrophy 1 (OPA1) in old NHFs decreased OCR and shifted metabolism more toward glycolysis. Downregulation of MFN1 and OPA1 also suppressed the radiation‐induced increase in doubling time of NHFs. In summary, results show that a metabolic shift from glycolysis in young to mitochondrial respiration in old NHFs occurs during chronological lifespan, and MFN1 and OPA1 regulate this process.