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Human corneal epithelial cells internalize Aspergillus flavus spores by actin mediated endocytosis

ABSTRACT: Mycotic leratitis is the corneal inflammation predominantly caused by Fusarium and Aspergillus species. Corneal epithelium is the earliest cell type encounter the invading pathogen. The innate immune responses of human corneal epithelial cells against Aspergillus flavus is not known. Here we studied the role of human corneal epithelial cells against Aspergillus flavus infection. The results showed that corneal epithelial cells internalized Aspergillus flavus conidia through actin mediated polymerization surrounding the conidia. Further the actin inhibitor cytochalasin D treatment reduced the formation actin ring around the conidia. The engulfed conidia acquired endosomal proteins as revealed by immunofluorescence analsyisis. Mass spectromtery of phagosomal proteins confirmed the recruitment of endosomal proteins and other proteins involved in phagocytosis. These results show the involvement of corneal epithelial cells in anti fungal defense.

INSTRUMENT(S): LTQ Orbitrap Velos

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Epithelial Cell, Cell Culture

DISEASE(S): Disease Free

SUBMITTER: Divya Arunachalam

LAB HEAD: Prof. K. Dharmalingam

PROVIDER: PXD019512 | Pride | 2021-04-07

REPOSITORIES: Pride

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Human Corneal Epithelial Cells Internalize Aspergillus flavus Spores by Actin-Mediated Endocytosis.

Arunachalam Divya D Namperumalsamy Venkatesh Prajna VP Prajna Lalitha L Kuppamuthu Dharmalingam D

Infection and immunity 20210517 6

Human corneal epithelial (HCE) cells play a significant role in the innate immune response by secreting cytokines and antimicrobial peptides when they encounter fungal pathogens. But the detailed mechanism of attachment and engulfment of the fungal conidia by HCE cells is not well understood. Here, we show the phagocytosis of <i>Aspergillus flavus</i> conidia by RCB2280 cells and primary HCE cultures using confocal microscopy and proteomic analysis of conidium-containing phagosomes. Phalloidin s ...[more]

PMID: 33753415

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Project description:A. flavus keratitis is one of the predominant fungal infections affecting the tropical parts of the world. Melanin is a virulence factor in numerous pathogenic fungi and the melanin layer maintains the cell wall structure and provides chemical and physical protection to the organism. However, the molecular and biological mechanisms modulating melanin-mediated host-pathogen interaction in A. flavus keratitis are not well understood. This work aimed to compare the morphology, surface proteome profile and virulence of melanized and non-melanized conidia of A. flavus. An environmental isolate and two clinical isolates were included in this study. L-DOPA melanin pathway-specific inhibitor kojic acid (KA) as used to prepare non-melanized conidia. Conidial surface proteins were extracted using 100% formic acid at 0 ºC and the extracted proteins were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS PAGE). Formic acid extracts were analyzed in an Orbitrap Velos pro-mass spectrometer. Conidial surface morphology difference was examined using scanning electron microscopy (SEM). Furthermore, lactophenol and calcofluor staining were performed to check the morphology and staining efficiency of melanized conidia (MC) and non-melanized conidia (NMC). A Galleria mellonella insect model was used to examine the virulence efficiency of MC and NMC. Kojic acid treatment inhibited melanin synthesis in A. flavus and the conidial surface protein profile was significantly different in kojic acid-treated non-melanized conidia. Several cell wall-associated proteins and proteins responsible for oxidative stress, carbohydrate, and chitin metabolic pathway were found only in the formic acid extracts of NMC. SEM analysis showed the conidial surface morphology difference between the NMC and MC indicating the role of melanin in the structural integrity of the conidial cell wall. The levels of calcofluor staining efficiency were different, but there was no microscopic morphology difference in lactophenol cotton blue staining of MC and NMC. Evaluation of virulence of MC and NMC in G. mellonella model showed NMC was less virulent compared to MC . Our results showed that the integrity of the conidial surface is controlled by the melanin layer. The alteration in the surface protein profile indicated that many surface proteins are masked by the melanin layer and hence melanin can modulate the host response by preventing the exposure of fungal proteins to the host immune defense system. G. mellonella in vivo virulence assay also confirmed that the non-melanized conidia were susceptible to host defense as in other Aspergillus pathogens.

			Action	DRS
	AD_HCE_1123_P1_B1_1.msf	Msf
	AD_HCE_1123_P1_B1_1.raw	Raw
	AD_HCE_1123_P1_B1_2.msf	Msf
	AD_HCE_1123_P1_B1_2.raw	Raw
	AD_HCE_1123_P1_B2_1.msf	Msf