Lawal Tomiwa, Chang Alana H, Carnley Lauren G, Celoge Nehry Y, Blount Taylor A, Vied Cynthia, Nemec Antonia A, Tomko Robert J
Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL, USA 32306.
Translational Science Laboratory, Florida State University College of Medicine, Tallahassee, FL, USA 32306.
bioRxiv. 2025 Aug 1:2025.07.31.666823. doi: 10.1101/2025.07.31.666823.
Intracellular pathogens frequently subjugate the ubiquitin system to evade host immune defenses and establish intracellular replication niches. Microsporidia are obligate intracellular animal parasites that typically cause self-limiting infections in humans, but can sometimes cause fatal disseminated disease. At present, the ubiquitin system of microsporidia is virtually unexplored. Here, we discover a likely effector deubiquitinase (DUB) of the otubain subgroup from the human pathogenic microsporidian , which we designate ehOTUB1. We find that ehOTUB1 selectively binds the human ubiquitin conjugating (E2) enzyme UBE2K and inhibits its ubiquitin conjugation activity independent of ehOTUB1 DUB activity. We show that ehOTUB1 obstructs docking of UBE2K onto ubiquitin E1 enzyme via steric conflict with ubiquitin in the E1 adenylation site to prevent ubiquitin transfer to UBE2K. This unconventional mechanism of E2 inhibition expands the known repertoire by which pathogens manipulate ubiquitin signaling, and suggests that direct inhibition of E2 enzymes may be a broader function of otubain subfamily DUBs than originally appreciated.
细胞内病原体常常利用泛素系统来逃避宿主免疫防御并建立细胞内复制龛。微孢子虫是专性细胞内动物寄生虫，通常在人类中引起自限性感染，但有时也会导致致命的播散性疾病。目前，微孢子虫的泛素系统几乎未被探索。在此，我们从人类致病微孢子虫中发现了一种otubain亚组的可能效应去泛素酶（DUB），我们将其命名为ehOTUB1。我们发现ehOTUB1选择性结合人类泛素结合（E2）酶UBE2K，并独立于ehOTUB1 DUB活性抑制其泛素结合活性。我们表明，ehOTUB1通过与E1腺苷化位点中的泛素发生空间冲突，阻碍UBE2K与泛素E1酶对接，从而防止泛素转移至UBE2K。这种E2抑制的非常规机制扩展了病原体操纵泛素信号传导的已知方式，并表明直接抑制E2酶可能是otubain亚家族DUBs比最初认识到的更广泛的功能。
