Role of cytomegalovirus gpUL132 on the cytoskeleton

Abstract

Human cytomegalovirus (HCMV) has been known to be a widespread pathogen in the human population. In most cases an infection remains asymptomatic and without consequences for its host. However, immunocompromised patients are at risk of suffering from severe complications like retinitis, colitis or in case of antenatal infections hearing losses or microcephaly. As treatment options are currently limited and associated with high levels of toxicity, new viral targets are needed to treat this growing group of patients. While the crucial role of glycoprotein UL132 (gpUL132), a viral tegument protein, for replication of HCMV has been known for some time, its underlying mechanisms remain elusive. A pronounced morphological and replicative defect in the cytoplasmic viral assembly complex (cVAC) has been described in the absence of gpUL132. This study aimed at better understanding the role of gpUL132 in cVAC biogenesis and viral replication. The emphasis was placed on the interaction between gpUL132 and cellular microtubules. The phenotype was controlled using a circularity assay. The quantitative role of gpUL132 in cVAC biogenesis was investigated with nocodazole washout assays. To control for protein concentrations as possible qualitative differences, Western blots were performed. In this study, it was shown that the cVAC defect observed with gpUL132-deficient viruses does not depend on noncentrosomal nucleation. Furthermore, an SxIP-motif found in gpUL132 did not exhibit any influence on cVAC morphology or nucleation. The protein concentrations did not indicate differences depending on the presence of gpUL132. A hitherto unknown decrease of intracellular calmodulin-regulated spectrin-associated protein 2 levels during late stage infections with gpUL132 competent mutant viruses was observed. Its role remains unclear. More work is needed to reveal the mechanisms of viral modulation of the cellular cytoskeleton.