Probing the interaction between the WDR41 7CD loop of the C9ORF72 complex and purified PQLC2

Abstract

The lysosomal cationic amino acid transceptor PQLC2 integrates transport with receptor-like signaling roles by recruiting the C9ORF72/SMCR8/WDR41 (CSW) complex in response to cellular cationic amino acid depletion. CSW recruitment depends on the interaction of PQLC2 with a disordered loop (7CD loop) extending from the WDR41 {beta}-propeller. Defining the molecular basis of this interaction is therefore essential for understanding how PQLC2 connects cellular amino acid availability to downstream signaling. Here, we used site-directed electron paramagnetic resonance (EPR) spectroscopy to characterize the interaction between purified PQLC2 and a synthetic WDR41 7CD loop peptide containing a site-specific nitroxide spin label. Using a consensus mutagenesis strategy, we stabilized detergent-purified PQLC2 and found that it assembles as a homotrimer, similar to other PQ-loop transporters. EPR experiments demonstrated the direct and specific association of the 7CD loop with PQLC2, and highlighted the key role of the the central region of the 7CD loop to establish this interaction via conserved aromatic residues. Spin labels introduced at different positions further provided local structural and dynamic information of the 7CD loop upon PQLC2 binding. The data supports a model in which the central region of the loop is anchored within the cytosolic cavity of PQLC2, whereas the flanking regions, which are dispensable for binding, retain substantial conformational flexibility. Together, we provide a direct biochemical evidence for PQLC2/WDR41 7CD loop recognition, a step forward towards understanding the transceptor mechanism of PQLC2.

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BibTeX RIS

BibTeX

@misc{jamal2026probing,
  title = {{Probing the interaction between the WDR41 7CD loop of the C9ORF72 complex and purified PQLC2}},
  author = {L. Jamal and P. von Gaudecker and L. Pieri and C. Ransy and N. Nakamae and F. Andre and I. Tascon and H. Jiang and B. Ochoa-Lizarralde and I. Ubarretxena-Belandia and C. Debacker and B. Gasnier and L. C. Tabares and J. L. Vazquez-Ibar},
  howpublished = {bioRxiv},
  year = {2026},
  month = sep,
  doi = {10.64898/2026.09.18.752389},
  url = {https://www.biorxiv.org/content/10.64898/2026.09.18.752389v1},
  note = {CC BY-NC},
}

RIS

TY  - UNPB
TI  - Probing the interaction between the WDR41 7CD loop of the C9ORF72 complex and purified PQLC2
AU  - L. Jamal
AU  - P. von Gaudecker
AU  - L. Pieri
AU  - C. Ransy
AU  - N. Nakamae
AU  - F. Andre
AU  - I. Tascon
AU  - H. Jiang
AU  - B. Ochoa-Lizarralde
AU  - I. Ubarretxena-Belandia
AU  - C. Debacker
AU  - B. Gasnier
AU  - L. C. Tabares
AU  - J. L. Vazquez-Ibar
PY  - 2026
DA  - 2026/09/18
PB  - bioRxiv
DO  - 10.64898/2026.09.18.752389
UR  - https://www.biorxiv.org/content/10.64898/2026.09.18.752389v1
AB  - The lysosomal cationic amino acid transceptor PQLC2 integrates transport with receptor-like signaling roles by recruiting the C9ORF72/SMCR8/WDR41 (CSW) complex in response to cellular cationic amino acid depletion. CSW recruitment depends on the interaction of PQLC2 with a disordered loop (7CD loop) extending from the WDR41 {beta}-propeller. Defining the molecular basis of this interaction is therefore essential for understanding how PQLC2 connects cellular amino acid availability to downstream signaling. Here, we used site-directed electron paramagnetic resonance (EPR) spectroscopy to characterize the interaction between purified PQLC2 and a synthetic WDR41 7CD loop peptide containing a site-specific nitroxide spin label. Using a consensus mutagenesis strategy, we stabilized detergent-purified PQLC2 and found that it assembles as a homotrimer, similar to other PQ-loop transporters. EPR experiments demonstrated the direct and specific association of the 7CD loop with PQLC2, and highlighted the key role of the the central region of the 7CD loop to establish this interaction via conserved aromatic residues. Spin labels introduced at different positions further provided local structural and dynamic information of the 7CD loop upon PQLC2 binding. The data supports a model in which the central region of the loop is anchored within the cytosolic cavity of PQLC2, whereas the flanking regions, which are dispensable for binding, retain substantial conformational flexibility. Together, we provide a direct biochemical evidence for PQLC2/WDR41 7CD loop recognition, a step forward towards understanding the transceptor mechanism of PQLC2.
ER  -

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