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bioRxiv · 10.64898/2025.12.22.695975

Molecular insights into Profilin1-dependent regulation of cellular phosphatidylinositol-(4,5)-bisphosphate

Orenberg, A.·Chirumbolo, M.·Eder, I.·Liu, J.-J.·Liu, S.·Gau, D.·Tang, Y.·Rottner, K.·Luo, J.·Hammond, G. R.·Roy, P.
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Abstract

Phosphatidylinositol (4,5)-bisphosphate (PIP2), the most abundant cellular poly-phosphoinositide (PPI) class of phospholipid, is a central plasma membrane (PM)-associated signaling hub that controls many cellular processes. In this study, we demonstrate that either deletion of the gene encoding actin-binding protein profilin1 (Pfn1) or disruption of Pfn1-actin interaction leads to downregulation of PM PIP2 content in cells. This is also phenocopied when F-actin is depolymerized implying that Pfn1-dependent PIP2 alteration is related to its actin-regulatory function. Phospholipase C (PLC) activity is critical for Pfn1-deficient cells to exhibit the PIP2-related phenotype. These findings, taken together with biochemical signatures of elevated PIP2 hydrolysis (higher baseline PM diacylglycerol-to PIP2 ratio and protein kinase C activity) exhibited by Pfn1-deficient cells, imply that PLC-mediated PIP2 hydrolysis plays a role in Pfn1-dependent regulation of PM PIP2. Furthermore, we unexpectedly found that Pfn1 loss leads to dramatic alterations in several other important forms of lipids, revealing a previously unrecognized role of Pfn1 as a broad regulator of cellular lipid environment that extends beyond PPI control. In conclusion, our study establishes Pfn1 as an important regulator of cellular lipid homeostasis. SUMMARY STATEMENTThis study uncovers a mechanism of how functional loss of Profilin1, a key regulator of actin cytoskeleton, can trigger downregulation of plasma membrane content of PIP2, an important class of phospholipid, in cells.

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Orenberg, A., Chirumbolo, M., Eder, I., Liu, J.-J., Liu, S., Gau, D., Tang, Y., Rottner, K., Luo, J., Hammond, G. R., Roy, P.. 2025-12-23. Molecular insights into Profilin1-dependent regulation of cellular phosphatidylinositol-(4,5)-bisphosphate. https://doi.org/10.64898/2025.12.22.695975

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