Calpain-1 knockout reveals broad effects on erythrocyte deformability and physiology

Pharmacological inhibitors of cysteine proteases have provideduseful insights into the regulation of calpain activity inerythrocytes. However, the precise biological function of calpainactivity in erythrocytes remains poorly understood. Erythrocytesexpress calpain-1, an isoform regulated by calpastatin, theendogenous inhibitor of calpains. In the present study, weinvestigated the function of calpain-1 in mature erythrocytes usingour calpain-1-null [KO (knockout)] mouse model. The calpain-1gene deletion results in improved erythrocyte deformabilitywithout any measurable effect on erythrocyte lifespan in vivo.The calcium-induced sphero-echinocyte shape transition iscompromised in the KO erythrocytes. Erythrocyte membraneproteins ankyrin, band 3, protein 4.1R, adducin and dematin aredegraded in the calcium-loaded normal erythrocytes but not inthe KO erythrocytes. In contrast, the integrity of spectrin andits state of phosphorylation are not affected in the calciumloadederythrocytes of either genotype. To assess the functionalconsequences of attenuated cytoskeletal remodelling in the KOerythrocytes, the activity of major membrane transporters wasmeasured. The activity of the K+\u2013Cl 12 co-transporter and theGardos channel was significantly reduced in the KO erythrocytes.Similarly, the basal activity of the calcium pump was reducedin the absence of calmodulin in the KO erythrocyte membrane.Interestingly, the calmodulin-stimulated calcium pump activitywas significantly elevated in the KO erythrocytes, implying awider range of pump regulation by calcium and calmodulin. Takentogether, and with the atomic force microscopy of the skeletalnetwork, the results of the present study provide the first evidencefor the physiological function of calpain-1 in erythrocytes withtherapeutic implications for calcium imbalance pathologies suchas sickle cell disease

An overview of transmission theory and techniques of large-scale antenna systems for 5G wireless communications

To meet the future demand for huge traffic volume of wireless data service, the research on the fifth generation (5G) mobile communication systems has been undertaken in recent years. It is expected that the spectral and energy efficiencies in 5G mobile communication systems should be ten-fold higher than the ones in the fourth generation (4G) mobile communication systems. Therefore, it is important to further exploit the potential of spatial multiplexing of multiple antennas. In the last twenty years, multiple-input multiple-output (MIMO) antenna techniques have been considered as the key techniques to increase the capacity of wireless communication systems. When a large-scale antenna array (which is also called massive MIMO) is equipped in a base-station, or a large number of distributed antennas (which is also called large-scale distributed MIMO) are deployed, the spectral and energy efficiencies can be further improved by using spatial domain multiple access. This paper provides an overview of massive MIMO and large-scale distributed MIMO systems, including spectral efficiency analysis, channel state information (CSI) acquisition, wireless transmission technology, and resource allocation