Proteomic Insights Reveal TpSH3A with Dual Roles in Cellulases and Oxidative Stress Response in Talaromyces Pinophilus.

SH3 domain-containing proteins mediate protein-protein interactions, facilitate membrane localization, and regulate intracellular signaling pathways in eukaryotes. Although cellulolytic fungi harbor multiple SH3-containing proteins, their roles in cellulase secretion and stress adaptation have never been studied. This study identified 25 SH3-domain-containing proteins in the model cellulolytic filamentous fungus Talaromyces pinophilus. Transcriptomic analysis further revealed a FUS1p homolog SH3 protein, TpSH3A, which was uniquely downregulated in the presence of cellulose. Functional characterization of TpSH3A using knockout and complementation analyses demonstrated that deletion of Tpsh3a adversely affects fungal growth, while concomitantly enhancing the secretion of cellulose-degrading enzymes. Interestingly, the ΔTpsh3a strain exhibited pronounced sensitivity to oxidative and endoplasmic reticulum stress, as evidenced by impaired growth under allyl alcohol and hydrogen peroxide, an attenuated unfolded protein response, and dysregulated reactive oxygen species homeostasis. Quantitative differential proteomic analysis showed coordinated downregulation of proteins involved in respiration, ATP generation, and the unfolded protein response, along with upregulation of β-glucosidases, indicating a role in cellular energy metabolism and secretory output. In concordance, pull-down analyses suggested that TpSH3A interacts with proteins involved in oxidative phosphorylation, intracellular transport, and membrane organization. These findings highlight TpSH3A as an important factor linking environmental sensing with enzyme secretion, optimizing T. pinophilus's capacity for biomass degradation.