摘要
Physiological aging imposes significant alterations in the repertoire of T cells and all associated functions.Although several studies have reported defects upon antigen-induced activation of T cells during aging,the molecular mechanisms that control T-cell receptor(TCR)downmodulation remain to be fully defined.While previous studies have assessed the role of F-actin in regulating activation-induced TCR internalization,few have delineated the roles of motor proteins,such as non-muscle myosin IIA(NMMIIA).In this study,we describe a series of experiments supporting the hypothesis that effective TCR downmodulation requires not only efficient reorganization of the actin cytoskeleton,but also functional NMMIIA.For the first time,we show that CD41 T cells from elderly human donors have dysfunctional NMMIIA that contributes to delaying activation-induced TCR internalization and impairing calcium mobilization.Additionally,our results demonstrate that chemical inhibition of NMMIIA in CD41 T cells from young donors also results in complete abrogation of TCR internalization,strongly supporting the fundamental role of NMMIIA in modulating this event.Recent observations that the generation of an efficient T-cell response requires migration prompted us to investigate whether NMMIIA also plays a regulatory role in CD41 T-cell migration.We show that chemical inhibition of NMMIIA downmodulates chemotactic migration in CD41 T cells from both young and elderly donors.Together,these data demonstrate a significant contribution of dysfunctional NMMIIA to TCR-mediated functional defects during aging.
基金
grants RO1AG030599 and RO1AG025220 to UP,UAMS Graduate student research fund to SC,and National Center for Research Resources UL1RR029884 to the CCTR.The authors declare no conflicts of interest.We thank Mrs Michela Palmieri at the University of Arkansas for Medical Science for technical assistance in coordinating human subjects for the study and for T-cell isolation.We acknowledge support from the CCTR at UAMS for phlebotomy.Thanks are also due to Dr Steven Barger,Department of Geriatrics at the University of Arkansas for Medical Sciences,for help with assays involving intracellular calcium flux,and Dr Martin Cannon,Department of Microbiology and Immunology at the University of Arkansas for Medical Sciences,for flow cytometry analyses and advice.
