Context

Cell migration underlies numerous physiological processes_ from tissue development to wound repair—and is equally central to pathological events such as cancer metastasis. Migrating cells typically display a well-established front-rear polarity, alternating between protrusion and contraction. Yet despite decades of work, how cells convert mechanical forces (mechanosensing) into dynamic polarization remains incompletely understood.

In our new study, Singh et al. (https://www.nature.com/articles/s41467-025-67090-z), we identify caveolae as the crucial missing link between membrane tension and directional cell movement. Caveolae are specialized plasma membrane invaginations composed of caveolin-1 (Cav1) and associated cavin proteins. Long involved in membrane trafficking and lipid organization, caveolae have more recently emerged as fundamental mechanosensors and mechanoprotectors^1,2. Their ability to flatten and disassemble under tension provide a rapid membrane reservoir while simultaneously triggering mechanotransduction.

 Caveolae asymmetry guides cell direction

Our initial experiments observing caveolae in freely migrating Hs578t triple negative breast cancer cells visualized a consistent asymmetry: caveolae were scarce at the high-tension front (protrusion) and enriched at the low-tension rear (contraction).

 A serendipitous observation during spontaneous reorientation

A pivotal moment came from watching cells spontaneously change direction with no external cues or manipulations. We observed that the very first event accompanying reorientation was the loss of caveolae front–rear asymmetry. This collapse in asymmetry causing migration to stall. Only after the polarity re-established, did cells resume movement, defining a new rear and a new migration axis.

This accidental observation motivated a series of controlled experiments. By forcing cells to change direction on straight-line or Z-shaped micropatterns, we repeatedly observed the same sequence of events, reinforcing the idea that caveolae asymmetry is an early and essential determinant of directionality.

Membrane tension is the master regulator

Using the membrane tension reporter Flipper-TR, we established that migrating cells intrinsically possess a front-rear tension gradient: higher at the front and lower tension at the rear. This gradient directly explains caveolae asymmetry—high tension drives caveolae disassembly into Cav1 scaffolds, whereas low tension allows caveolae to remain budded.

Our lab previously showed that caveolae flatten and disassemble in response to increased membrane tension¹. We wondered how the intrinsic tension gradient would behave under acute mechanical stress.  A global increase in tension (hypo-osmotic shock) abolished the gradient, selectively disassembling rear caveolae and halting migration. When membrane tension recovered, caveolae polarity returned and migration resumed.

Similarly, optogenetic activation of PI3K specifically at the rear locally increased membrane tension, causing immediate Cav1 disassembly and migration arrest. These experiments confirmed that membrane tension directly regulate caveolae dynamics and thus cell migration.

Caveolae asymmetry regulates RhoA signaling and contractility

Super-resolution STORM imaging revealed a structural polarity: budded caveolae populate the rear, whereas Cav1 scaffolds (S1A and S1B populations) are enriched at the front. In parallel, control cells showed higher levels of active RhoA at the rear—a polarity completely lost in Cav1-KO and cavin1-KO cells. Thus, bona fide caveolae and their asymmetric distribution are required to maintain RhoA activity gradients.

A tension-Caveolae-RhoA feedback loop

Raising membrane tension reduced active RhoA specifically at the rear in control cells. This sensitivity was absent in Cav1-KO cells but rescued by Cav1 re-expression. This demonstrates that caveolae mechanosensing regulates active RhoA polarity during mechanical challenge.

 Biochemically, we found that active RhoA preferentially associates with Cav1 scaffolds at the front under high tension. We propose that Cav1 scaffolds sequester RhoA-GTP at the front to prevent inappropriate contraction, while effective contractility requires rear -localized budded caveolae.

 Budded caveolae drive efficient actomyosin contraction

We asked whether these distinct Cav1 structures have functional consequences for contractility. Control cells showed ~ 2.4 contraction events per hour. This dropped to 0.9 events/hour in cavin1-KO cells (having only Cav1 scaffolds but lacking budded caveolae) and 0.4 events/hour in Cav1-KO cells. Reintroducing Cav1 restored high contraction rates.

These results indicate that although RhoA-GTP may interact with scaffolds, only budded caveolae can potentiate Rho1 activity sufficiently to drive robust actomyosin contraction.

Coupling with RhoGEFs

The functional specificity of budded caveolae and Cav1 scaffolds appears to stem from their coupling with RhoA-GEFs such as ARHGEF25 and ARHGEF11. Using optogenetics, we found that Cav1 intensity peaks coincides precisely with ARHGEF25 recruitment and the onset of rapid contraction in wild-type cells. This coupling is lost in cavin1-KO and Cav1-KO cells, resulting in delayed contraction dynamics.

Temporal hierarchy: caveolae assembly precedes RhoA activation

Time-resolved analyses showed that caveolae assemble ~ 2 minutes before local RhoA activation at contraction sites. This temporal hierarchy strongly supports the idea that caveolae act upstream, enabling GEF recruitment and initiating contractile events that shape cell directionality.

 A physical model explaining directional persistence.

To generalize these findings, we developed a minimal physical model of cell motility incorporating tension-contractility feedback. The model shows that when contraction probability depends on local tension (mediated by caveolae sensing), directional persistence increases dramatically compared with a simple random walk. This supports our experimental finding that caveolae-driven feedback amplifies short-term directional persistence.

Final Takeaways.

• Caveolae provide the mechanotransduction link between membrane tension and cell directionality.
• Front-rear Cav1 asymmetry is essential: budded caveolae at rear and Cav1 scaffolds at front.
• This structural polarization supports RhoA polarity, enabling high rear contractility and preventing front contraction.
• Budded caveolae are spatiotemporally coupled to RhoGEFs, triggering efficient actomyosin contraction and persistent migration.
• Cav1 scaffolds at the front interacts with RhoA-GTP but are not coupled with RhoGEFs, thereby preventing unwanted contraction at the protruding front.

Together, these discoveries uncover a robust mechanotransduction pathway in which caveolae dynamics integrate physical forces with biochemical signaling to guide cell navigation

References.

1. Sinha, B. et al. Cells respond to mechanical stress by rapid disassembly of caveolae. Cell 144, 402–413 (2011).
2. Dewulf, M. et al. Dystrophy-associated caveolin-3 mutations reveal that caveolae couple IL6/STAT3 signaling with mechanosensing in human muscle cells. Nat Commun 10, (2019).