Serum Response Factor Regulates Immediate Early Host Gene Expression in Toxoplasma gondii-Infected Host Cells

Toxoplasma gondii is a wide spread pathogen that can cause severe and even fatal disease in fetuses and immune-compromised hosts. As an obligate intracellular parasite, Toxoplasma must alter the environment of its host cell in order to establish its replicative niche. This is accomplished, in part, by secretion of factors into the host cell that act to modulate processes such as transcription. Previous studies demonstrated that genes encoding transcription factors such as c-jun, junB, EGR1, and EGR2 were amongst the host genes that were the most rapidly upregulated following infection. In cells stimulated with growth factors, these genes are regulated by a transcription factor named Serum Response Factor. Serum Response Factor is a ubiquitously expressed DNA binding protein that regulates growth and actin cytoskeleton genes via MAP kinase or actin cytoskeletal signaling, respectively. Here, we report that Toxoplasma infection leads to the rapid activation of Serum Response Factor. Serum Response Factor activation is a Toxoplasma-specific event since the transcription factor is not activated by the closely related protozoan parasite, Neospora caninum. We further demonstrate that Serum Response Factor activation requires a parasite-derived secreted factor that signals via host MAP kinases but independently of the host actin cytoskeleton. Together, these data define Serum Response Factor as a host cell transcription factor that regulates immediate early gene expression in Toxoplasma-infected cells

Distance perception

Distance perception refers to a process in which an observer perceives an interval between two points in space. The interval does not have to be linear, but perception of a straight-line distance has been most extensively studied. The distance can be defined between the observer and an external object (egocentric distance) or between two external objects (exocentric distance), and perception of these two types of distance tends to show different characteristics (e.g., Loomis et al. 1992). Distance perception and depth perception are often considered synonymous. However, they can also be subtly distinguished such that depth perception specifically refers to perception of exocentric distance along the observer’s line of sight. Although this entry is focused on visual distance perception, distance can be perceived through multiple senses, such as audition (Kolarik et al. 2016), haptics (Lederman and Klatzky 2009), and vestibular sense and proprioception ( ..