Phosphoinositide signaling

The National Institute of General Medical Sciences awarded the University of Illinois $415,788 on July 1, 2026, under the Biomedical Research and Research Training program (CFDA 93.859) to investigate phosphoinositide regulation of Rho guanine nucleotide exchange factors and their role in autophagy signaling.

The research addresses a gap in understanding how phosphoinositides regulate the DBL family of RhoGEFs, guanine nucleotide exchange factors that contain pleckstrin homology domains. The investigator's prior work showed that more than 50 percent of human pleckstrin homology domain-containing proteins likely bind phosphoinositides with specificity—substantially higher than the previously understood rate of approximately 10 percent. The project focuses on deciphering regulatory mechanisms by which phosphoinositides, particularly PI(3,5)P2 on late endosomes and lysosomes, control RhoGEF function in autophagosome maturation. Dysregulation of PI(3,5)P2 biogenesis has been associated with defective autophagy and multiple human pathologies.

Work is performed at the University of Illinois, Urbana, Illinois. The award runs from July 1, 2026, through March 31, 2031. The assistance type is a Project Grant.

Abstract

Phosphoinositides (pips) are minor components of the eukaryotic membrane but major regulators of cellular functions. The seven pips are critically involved in nearly every aspect of cell physiology. The pleckstrin homology (PH) domains constitute the largest family of putative lipid-binding protein domains, present in over 250 human proteins that are involved in a wide range of signaling pathways and functions. However, IT was thought that recognition of specific pips by PH domains only occurred in ~10% of these proteins. Our recent work has challenged this view and found that >50% of the human PH domain-containing proteins likely bind pips with specificity. This revelation has brought to the forefront a significant GAP in our knowledge of regulation of signaling proteins by pips. One of the subfamilies of PH domain-containing proteins is the DBL family of RHO guanine nucleotide exchange factors (rhogefs), each with a PH domain following the catalytic domain. Only a handful of these rhogefs have been reported to be regulated by specific pips, and yet we have found many of the ~70 members to bind or predicted to bind pips with specificity, suggesting the existence of important regulatory mechanisms yet to be discovered. Our current investigation and this proposed research program will focus on deciphering those mechanisms of rhogef regulation. One of the cellular processes regulated by pips is autophagy, a process essential for a broad range of cellular functions and tissue development, and dysregulated in many human diseases. Found on late endosomes and lysosomes, PI(3,5)P2 is necessary for autophagosome maturation, and dysregulation of PI(3,5)P2 biogenesis has been linked to several human pathologies through defective autophagy. However, the mechanism by which PI(3,5)P2 regulates autophagy is poorly understood. Our study of PIP regulation of rhogefs has uncovered strong candidates for effectors of PI(3,5)P2 in the regulation of autophagy, which will be investigated in the proposed program. Furthermore, adult skeletal muscle regeneration in which autophagy plays an indispensable role will be studied as a physiological context for the molecular mechanisms to be deciphered. This research program employs a multidisciplinary approach encompassing biochemistry, biophysics, cell biology, and mouse models, all of which within the PI's expertise and supported by our strong track record of productivity and innovation. Knowledge gained is expected to have a significant impact on the molecular understanding of lipid signaling, autophagy, and muscle regeneration.