Prabhakar Pradhan

MUC13 interaction with receptor tyrosine kinase HER2 drives pancreatic ductal adenocarcinoma progression

Although MUC13, a transmembrane mucin, is aberrantly expressed in pancreatic ductal adenocarcinoma (PDAC) and generally correlates with increased expression of HER2, the underlying mechanism remains poorly understood. Herein, we found that MUC13 co-localizes and interacts with HER2 in PDAC cells (reciprocal co-immunoprecipitation, immunofluorescence, proximity ligation, co-capping assays) and tissues (immunohistofluorescence). The results from this study demonstrate that MUC13 functionally interacts and activates HER2 at p1248 in PDAC cells, leading to stimulation of HER2 signaling cascade, including ERK1/2, FAK, AKT and PAK1 as well as regulation of the growth, cytoskeleton remodeling and motility, invasion of PDAC cells—all collectively contributing to PDAC progression. Interestingly, all of these phenotypic effects of MUC13–HER2 co-localization could be effectively compromised by depleting MUC13 and mediated by the first and second EGF-like domains of MUC13. Further, MUC13–HER2 co-localization also holds true in PDAC tissues with a strong functional correlation with events contributing to increased degree of disorder and cancer aggressiveness. In brief, findings presented here provide compelling evidence of a functional ramification of MUC13–HER2: this interaction could be potentially exploited for targeted therapeutics in a subset of patients harboring an aggressive form of PDAC.

Spatial temperature gradients guide axonal outgrowth

Formation of neural networks during development and regeneration after injury depends on accuracy of axonal pathfinding, which is primarily believed to be influenced by chemical cues. Recently, there is growing evidence that physical cues can play crucial role in axonal guidance. However, detailed mechanism involved in such guidance cues is lacking. By using weakly-focused near-infrared continuous wave (CW) laser microbeam in the path of an advancing axon, we discovered that the beam acts as a repulsive guidance cue. Here, we report that this highly-effective at-a-distance guidance is the result of a temperature field produced by the near-infrared laser light absorption. Since light absorption by extracellular medium increases when the laser wavelength was red shifted, the threshold laser power for reliable guidance was significantly lower in the near-infrared as compared to the visible spectrum. The spatial temperature gradient caused by the near-infrared laser beam at-a-distance was found to activate temperature-sensitive membrane receptors, resulting in an influx of calcium. The repulsive guidance effect was significantly reduced when extracellular calcium was depleted or in the presence of TRPV1-antagonist. Further, direct heating using micro-heater confirmed that the axonal guidance is caused by shallow temperature-gradient, eliminating the role of any non-photothermal effects.

Quantitative analysis of nanoscale intranuclear structural alterations in hippocampal cells in chronic alcoholism via transmission electron microscopy imaging

Chronic alcoholism is known to alter the morphology of the hippocampus, an important region of cognitive function in the brain. Therefore, to understand the effect of chronic alcoholism on hippocampal neural cells, we employed a mouse model of chronic alcoholism and quantified intranuclear nanoscale structural alterations in these cells. Transmission electron microscopy (TEM) images of hippocampal neurons were obtained, and the degree of structural alteration in terms of mass density fluctuation was determined using the light-localization properties of optical media generated from TEM imaging. The results, which were obtained at length scales ranging from ~30 to 200 nm, show that 10-12 week-old mice fed a Lieber-DeCarli liquid (alcoholic) diet had a higher degree of structural alteration than control mice fed a normal diet without alcohol. The degree of structural alteration became significantly distinguishable at a sample length of ~100 nm, which is the typical length scale of the building blocks of cells, such as DNA, RNA, proteins and lipids. Interestingly, different degrees of structural alteration at such length scales suggest possible structural rearrangement of chromatin inside the nuclei in chronic alcoholism.