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Both stimuli altered >200 proteins, sharing 25 upregulated and 2 downregulated proteins, yet also produced opposing regulation in several targets. AprA increased phosphorylation of 15 proteins and reduced phosphorylation of 36; polyP increased 12 and decreased 12. Unexpectedly, RNA metabolism and ribosome-related proteins were phosphorylated differently, while Ras-pathway components such as RipA and RacGEF GxcT were reduced. Mutants lacking RipA or GxcT failed to respond to both stimuli, supporting partially overlapping chemorepulsion mechanisms.",{"@graph":14,"@context":72},[15,34,55],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/research-report/","Research & 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Response to Two Different Chemorepellents  \nSalman Zahir Uddin 1, Ramesh Rijal 1,2, Darrell Pilling 1 and Richard H. Gomer 1, *  \nAcademic Editor: Francisco Rivero  \nReceived: 30 October 2025  \nRevised: 19 December 2025  \nAccepted: 24 December 2025  \nPublished: 29 December 2025  \nCopyright: © 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.  \n1 Department of Biology, Texas A&M University, ILSB 301 Old Main Drive, College Station, TX 77843-3474, USA; [szuddin@tamu.edu](szuddin@tamu.edu) (S.Z.U.); [ramesh.rijal@usm.edu](ramesh.rijal@usm.edu) (R.R.); [dpilling@bio.tamu.edu](dpilling@bio.tamu.edu) (D.P.)  \n2 School of Biological, Environmental, and Earth Sciences, University of Southern Mississippi, Hattiesburg, MS 39406, USA  \n* Correspondence: [rgomer@bio.tamu.edu](rgomer@bio.tamu.edu); Tel.: +1-979-458-5745  \nAbstract  \nChemorepulsion mechanisms for eukaryotic cells are poorly understood. We performed proteomics and phosphoproteomics to elucidate how Dictyostelium discoideum responds to its two endogenous chemorepellent signals, the protein AprA and inorganic polyphosphate (polyP). AprA and polyP affected levels of more than 200 proteins, with an overlap of both upregulating 25 proteins and downregulating two proteins. Two proteins were upregulated by AprA but downregulated by polyP, while two others showed the opposite trend. Surprisingly, many of the AprA-and polyP-regulated proteins are associated with RNA metabolism and ribosomes. AprA increased phosphorylation of 15 proteins and decreased phosphorylation of 36 proteins. PolyP increased phosphorylation of 12 proteins and decreased phosphorylation of 12 proteins. As expected, the two chemorepellents affected phosphorylation of signal transduction/ motility proteins, but unexpectedly affected phosphorylation of RNA-associated proteins. Both AprA and polyP decreased phosphorylation of five proteins including the Ras-interacting protein RipA and guanine nucleotide exchange factors (GEFs) such as the RacGEF GxcT. Mutants lacking RipA or GxcT were unresponsive to both AprA and polyP chemorepulsion. Together, this work supports the idea that rather than activating the same chemorepulsion mechanism, AprA and polyP activate only partially overlapping chemorepulsion mechanisms, and identifies two new components that are used by both chemorepellents.  \nKeywords: proteomics; phosphoproteomics; Dictyostelium discoideum; chemorepulsion; small GTPases; AprA; polyphosphate  \n1. Introduction  \nDirected cell migration is a fundamental biological process essential for morphogenesis, tissue repair, and immune surveillance [1,2] . While the molecular mechanisms of chemoattraction, the process by which cells migrate toward stimuli, have been extensively studied, the opposite behavior, chemorepulsion, remains comparatively underexplored [2,3] . Chemorepulsion enables cells to migrate away from harmful or crowded environments and plays vital roles in immune regulation, inflammation resolution, and spatial patterning during development [4,5] .  \nThe social amoeba D. discoideum is a well-established eukaryotic model organism for investigating chemotaxis due to its genetic tractability and the conservation of many signaling pathways with higher eukaryotes [6,7] . In this system, two endogenous chemorepellents have been identified: AprA, a ~60 kDa secreted autocrine protein, and inorganic polyphosphate (polyP), a polymer of phosphate [8–12] . The two repellents can function independently, but both cause cells at the edge of a colony to move away from the colony, presumably to find sources of food. In D. discoideum and other systems, a localized activation of Ras at one sector of the cell membrane activates pseudopod formation and movement in th","cbCaitAUvOk31LFY","https://ap.wps.com/l/cbCaitAUvOk31LFY","pdf",1992858,"English","# Abstract\n# Introduction","[{\"question\":\"What two endogenous chemorepellents are examined in Dictyostelium discoideum?\",\"answer\":\"The study examines AprA, a secreted autocrine protein, and inorganic polyphosphate (polyP), a polymer of phosphate.\"},{\"question\":\"How do AprA and polyP overlap in their effects on protein regulation?\",\"answer\":\"Both affect more than 200 proteins, with an overlap that includes 25 proteins upregulated and 2 proteins downregulated.\"},{\"question\":\"What phosphorylation changes do AprA and polyP produce?\",\"answer\":\"AprA increases phosphorylation of 15 proteins and decreases phosphorylation of 36, while polyP increases phosphorylation of 12 proteins and decreases phosphorylation of 12 proteins.\"}]","Phosphoproteomic Profiling Reveals Overlapping and Distinct Signaling Pathways in Dictyostelium discoideum in Response to Two Different Chemorepellents | PDF",1790769616,48]