Summary
A bioRxiv preprint reports that the protein PBF/PTTG1IP helps coordinate cell adhesion, front–rear polarity and directional movement. The findings come from mouse fibroblasts and human thyroid cancer cells, making them preclinical mechanistic evidence.
A bioRxiv preprint identifies the transmembrane protein PBF/PTTG1IP as a regulator of cell adhesion, polarity and directional movement. The study combined molecular profiling with experiments in mouse and human cell models to examine how cells coordinate their attachment to surrounding material with the organisation needed to migrate.
PBF has previously been studied mainly in pathological overexpression and cancer models. Its normal, or endogenous, cellular function has been less clear. The new work links PBF to focal adhesions—dynamic structures that connect a cell’s internal actin cytoskeleton to the extracellular matrix and help transmit mechanical and biochemical signals.
Evidence from mouse and human cell models
The researchers first analysed transcriptomic and phosphoproteomic profiles from cells overexpressing PBF. Separate enrichment analyses highlighted overlapping biological programmes involving cell adhesion, extracellular-matrix organisation, cytoskeletal regulation and cell motility.
They then used a Pbf knockout mouse model to test the protein’s function directly. Primary mouse embryonic fibroblasts lacking Pbf showed impaired migration and invasion, reduced adhesion to fibronectin and changes in the number, size and distribution of focal adhesions. Fibronectin is an extracellular-matrix protein that cells commonly use as an attachment surface in migration experiments.
The knockout cells also showed lower phosphorylation of FAK at tyrosine 397 and delayed formation of early adhesions. FAK, or focal adhesion kinase, is a signalling protein concentrated at focal adhesions; phosphorylation at Tyr397 is an established early event in focal-adhesion signalling.
The authors found related phenotypes in human thyroid cancer cells in which PBF was removed using CRISPR–Cas9. Conversely, reintroducing PBF into the Pbf-knockout mouse fibroblasts restored migration, supporting a direct connection between PBF loss and the observed movement defect.
Connecting adhesion to directional movement
Migration is not simply a matter of generating force. A moving cell must establish a front and rear, organise actin filaments, build and release adhesions in the right locations, and orient internal structures in the direction of travel. This front–rear organisation is called cell polarity.
Live-cell imaging showed altered actin organisation in the Pbf-knockout cells. Golgi-orientation assays also found impaired front–rear polarity. The Golgi apparatus normally becomes positioned toward the forward-facing side of many migrating cells, helping organise trafficking and cytoskeletal changes required for movement.
Together, the results place PBF at the intersection of three processes: formation of focal adhesions, organisation of cell polarity and directional motility. The authors propose that this provides a framework for understanding how abnormal PBF overexpression could contribute to invasive behaviour in cancer.
The study is a bioRxiv preprint reporting mechanistic experiments in cell models, rather than a clinical or patient-outcome study. Its findings support further investigation of PBF’s role in tumour biology and tissue movement, while whether the same mechanism operates in human tumours and can be targeted safely remains an open research question.