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<p>Profilins are conserved actin-binding proteins best known for their role in cytoskeletal dynamics. In plants, certain isoforms have been implicated in broader cellular processes, particularly during environmental stress. Here, we report that Arabidopsis thaliana profilin 1 (AtPFN1) exhibits previously uncharacterized ATP-independent foldase activity, capable of facilitating the refolding of denatured glucose-6-phosphate dehydrogenase (G6PDH). In vitro refolding assays demonstrated that AtPFN1 significantly enhanced G6PDH enzymatic recovery compared to spontaneous renaturation, highlighting a functional distinction from AtPFN2, which is known to act as an oligomeric holdase. Although AtPFN1 exists predominantly in a low molecular weight form, it was sufficient to catalyze substrate refolding. Intrinsic tryptophan fluorescence spectra further revealed structural features unique to AtPFN1, suggesting that its conformation favors transient substrate interactions. Expression analysis showed that AtPFN1 transcripts are rapidly upregulated by salicylic acid, jasmonic acid, and bacterial challenge, indicating its involvement in early stress signaling. Together, our findings demonstrate that AtPFN1 performs dual functions by regulating the actin cytoskeleton under normal conditions and facilitating stress-induced protein refolding, thus contributing to protein homeostasis under adverse environments.</p>

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Arabidopsis Profilin 1 Mediates ATP-independent Refolding of Misfolded Proteins Under Stress

  • 期刊论文

  • 发表日期：

    2025年7月28日

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  • Seong-Cheol Park,
  • Hye Song Lim,
  • Jung Ro Lee

摘要

Profilins are conserved actin-binding proteins best known for their role in cytoskeletal dynamics. In plants, certain isoforms have been implicated in broader cellular processes, particularly during environmental stress. Here, we report that Arabidopsis thaliana profilin 1 (AtPFN1) exhibits previously uncharacterized ATP-independent foldase activity, capable of facilitating the refolding of denatured glucose-6-phosphate dehydrogenase (G6PDH). In vitro refolding assays demonstrated that AtPFN1 significantly enhanced G6PDH enzymatic recovery compared to spontaneous renaturation, highlighting a functional distinction from AtPFN2, which is known to act as an oligomeric holdase. Although AtPFN1 exists predominantly in a low molecular weight form, it was sufficient to catalyze substrate refolding. Intrinsic tryptophan fluorescence spectra further revealed structural features unique to AtPFN1, suggesting that its conformation favors transient substrate interactions. Expression analysis showed that AtPFN1 transcripts are rapidly upregulated by salicylic acid, jasmonic acid, and bacterial challenge, indicating its involvement in early stress signaling. Together, our findings demonstrate that AtPFN1 performs dual functions by regulating the actin cytoskeleton under normal conditions and facilitating stress-induced protein refolding, thus contributing to protein homeostasis under adverse environments.