ABSTRACT
Aneuploidy, an incorrect number of chromosomes, is the leading cause of miscarriages and mental retardation in humans and is a hallmark of cancer. We examined the effects of aneuploidy on primary mouse cells by generating a series of cell lines that carry an extra copy of one of four mouse chromosomes. In all four trisomic lines, proliferation was impaired and metabolic properties were altered. Immortalization, the acquisition of the ability to proliferate indefinitely, was also affected by the presence of an additional copy of certain chromosomes. Our data indicate that aneuploidy decreases not only organismal but also cellular fitness and elicits traits that are shared between different aneuploid cells.
Subject(s)
Aneuploidy , Cell Proliferation , Gene Expression , Glucose/metabolism , Glutamine/metabolism , Trisomy , Animals , Cell Cycle , Cell Line , Cell Size , Cell Transformation, Neoplastic , Cellular Senescence , Culture Media , Embryo, Mammalian , Fibroblasts , Gene Dosage , Genomic Instability , Metabolic Networks and Pathways , Mice , Serial Passage , Translocation, GeneticABSTRACT
In response to bacterial infection, the neutrophil NADPH oxidase assembles on phagolysosomes to catalyze the transfer of electrons from NADPH to oxygen, forming superoxide and downstream reactive oxygen species (ROS). The active oxidase is composed of a membrane-bound cytochrome together with three cytosolic phox proteins, p40(phox), p47(phox), and p67(phox), and the small GTPase Rac2, and is regulated through a process involving protein kinase C, MAPK, and phosphatidylinositol 3-kinase. The role of p40(phox) remains less well defined than those of p47(phox) and p67(phox). We investigated the biological role of p40(phox) in differentiated PLB-985 neutrophils, and we show that depletion of endogenous p40(phox) using lentiviral short hairpin RNA reduces ROS production and impairs bacterial killing under conditions where p67(phox) levels remain constant. Biochemical studies using a cytosol-reconstituted permeabilized human neutrophil cores system that recapitulates intracellular oxidase activation revealed that depletion of p40(phox) reduces both the maximal rate and total amount of ROS produced without altering the K(M) value of the oxidase for NADPH. Using a series of mutants, p47PX-p40(phox) chimeras, and deletion constructs, we found that the p40(phox) PX domain has phosphatidylinositol 3-phosphate (PtdIns(3)P)-dependent and -independent functions. Translocation of p67(phox) requires the PX domain but not 3-phosphoinositide binding. Activation of the oxidase by p40(phox), however, requires both PtdIns(3)P binding and an Src homology 3 (SH3) domain competent to bind to poly-Pro ligands. Mutations that disrupt the closed auto-inhibited form of full-length p40(phox) can increase oxidase activity approximately 2.5-fold above that of wild-type p40(phox) but maintain the requirement for PX and SH3 domain function. We present a model where p40(phox) translocates p67(phox) to the region of the cytochrome and subsequently switches the oxidase to an activated state dependent upon PtdIns(3)P and SH3 domain engagement.
