Here, we describe a novel mechanism for the rapid regulation of surface levels of the neurotrophin receptor TrkB. Unlike nodose ganglion neurons, both retinal ganglion cells (RGCs) and spinal motor neurons (SMNs) in culture display only low levels of surface TrkB, though high levels are present intracellularly. Within minutes of depolarization or cAMP elevation, surface TrkB levels increase by nearly 4-fold, and this increase is not blocked by cycloheximide. These findings suggest that activity and cAMP elevation rapidly recruit TrkB to the plasma membrane by translocation from intracellular stores. We propose that a fundamental difference between peripheral nervous system (PNS) and central nervous system (CNS) neurons is the activity dependence of CNS neurons for responsiveness to their peptide trophic factors and that differences in membrane compartmentalization of the receptors underlie this difference.

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Lead halide perovskites have attracted tremendous research interests in the light-emitting field because of their high defect tolerance, solution processability, tunable spectrum, and efficient emission. In terms of luminescence types, both the narrowband emission derived from free-exciton (FE) and broadband white light emission from self-trapped exciton (STE) show great advantages in light-emitting applications. Despite the fascinating characteristics, their commercialization still suffers from the presence of toxic lead (Pb) and unsatisfactory stability. In this spotlight, we mainly focus on the lead-free candidates as phosphors for possible light-emitting applications. Thanks to the chemical diversity of metal halide perovskites and perovskite variants, many excellent lead-free light-emitting materials have recently been synthesized and characterized. We first classify these materials into three types according to material structures, including (1) double perovskites A2B­(I)­B­(III)­X6, (2) vacancy ordered perovskites A2B­(IV)­X6, (3) miscellaneous perovskite variants or halide semiconductors, which refer to halides without clear relation to the perovskite structure. We then highlight the importance of electronic dimensionality, defect passivation, and impurity doping in developing highly efficient perovskite-based emitters. We also discuss their applications in white light-emitting diodes (W-LED). Further challenges toward practical applications and potential applications are also included in a section on outlook and future challenges.