Biology subjects

Smith, A. O.

Publications and source records attributed to Smith, A. O..

3 recordsLinked to original sources

bioRxiv2026

Ift43 Controls the Ciliary Levels of Gli2 and Gli3

Intraflagellar transport (IFT) drives the bidirectional movement of trains composed of IFT-A, IFT-B, and BBSome complexes that build and maintain cilia while supporting their signaling functions. Over evolution, IFT became integral to Hedgehog signaling by directing the dynamic movements of receptors and Gli transcription factors that fine-tune pathway output. The IFT-A complex contains six subunits, but the smallest, Ift43, remains poorly characterized and is absent from many ciliated species, suggesting specialized roles in signaling rather than core ciliogenesis. Here we show that loss of Ift43 in mice causes mid-gestation lethality with severe craniofacial defects, exencephaly, abdominal wall defects with exposed viscera, edema, and limb patterning defects. At the cellular level, Ift43 deficiency reduces both the number and length of cilia and blocks induction of Gli1 following pathway activation by the agonist SAG. Although Smoothened relocalizes to cilia normally, Ift43 mutants abnormally accumulate Gli2 and Gli3 at ciliary tips before stimulation and continue to generate repressor forms after activation. Conversely, Ift43 overexpression increases basal Gli2 cleavage, revealing an unanticipated role for Ift43 in regulating Gli processing. Together, these findings identify Ift43 as a key IFT-A component that links ciliary assembly to Hedgehog signal transduction and helps set the balance between Gli activator and repressor forms.

cell biology↗

bioRxiv2025

Rag GTPases Suppress Renal Cystic Disease by Inhibiting TFEB Independently of mTORC1

Aberrant mTORC1 activation in renal tubular epithelial cells (rTECs) is implicated as a critical driver of renal cystic diseases (RCDs), including autosomal dominant polycystic kidney disease (ADPKD) and tuberous sclerosis (TSC), yet its precise role remains unclear. Rag GTPases recruit mTORC1 to lysosomes, its intracellular activation site. Unexpectedly, we found that deleting RagA/B in rTECs, despite inhibiting mTORC1, triggers renal cystogenesis and kidney failure. We identify TFEB as the key driver of cystogenesis downstream of RagA/B loss and show that Rag GTPases, rather than mTORC1, are the primary suppressors of TFEB in vivo. We further highlight increased nuclear TFEB as a shared feature of several RCD models, whereas differences in mTORC1 activity may explain the variable efficacy of mTORC1 inhibitors. Finally, we provide evidence that nuclear TFEB, rather than mTORC1 activation, is a more consistent biomarker of cyst-lining epithelial cells in ADPKD. Overall, these findings challenge the prevailing view that mTORC1 hyperactivation is required for renal cystogenesis, which has important translational implications. TeaserA serendipitous finding uncovers the Rag GTPases as strong suppressors of renal cystogenesis with important disease implications.

cell biology↗

bioRxiv2021

c-Jun N-terminal kinase (JNK) signaling contributes to cystic burden in polycystic kidney disease

Polycystic kidney disease is an inherited degenerative disease in which the uriniferous tubules are replaced by expanding fluid-filled cysts that ultimately destroy organ function. Autosomal dominant polycystic kidney disease (ADPKD) is the most common form, afflicting approximately 1 in 1,000 people. It primarily is caused by mutations in the transmembrane proteins polycystin-1 (Pkd1) and polycystin-2 (Pkd2). The most proximal effects of Pkd mutations leading to cyst formation are not known, but pro-proliferative signaling must be involved for the tubule epithelial cells to increase in number over time. The c-Jun N-terminal kinase (JNK) pathway promotes proliferation and is activated in acute and chronic kidney diseases. Using a mouse model of cystic kidney disease caused by Pkd2 loss, we observe JNK activation in cystic kidneys and observe increased nuclear phospho c-Jun in cystic epithelium. Genetic removal of Jnk1 and Jnk2 suppresses the nuclear accumulation of phospho c-Jun, reduces proliferation and reduces the severity of cystic disease. While Jnk1 and Jnk2 are thought to have largely overlapping functions, we find that Jnk1 loss is nearly as effective as the double loss of Jnk1 and Jnk2. Jnk pathway inhibitors are in development for neurodegeneration, cancer, and fibrotic diseases. Our work suggests that the JNK pathway should be explored as a therapeutic target for ADPKD. Author SummaryAutosomal dominant polycystic kidney disease is a leading cause of end stage renal disease requiring dialysis or kidney transplant. During disease development, the cells lining the kidney tubules proliferate. This proliferation transforms normally small diameter tubules into fluid-filled cysts that enlarge with time, eventually destroying all kidney function. Despite decades of research, polycystic kidney disease remains incurable. Furthermore, the precise signaling events involved in cyst initiation and growth remain unclear. The c-Jun N-terminal kinase (JNK), is a major pathway regulating cellular proliferation and differentiation but its importance to polycystic kidney disease was not known. We show that JNK activity is elevated in cystic kidneys and that reducing JNK activity decreases cyst growth pointing to JNK inhibition as a therapeutic strategy for treating polycystic kidney disease.

genetics↗