🧠 Background: What are Aquaporins (AQPs)?

• AQPs are membrane water channels that let water (and sometimes glycerol) move across cells — key for water balance in the body.
• They’re found in many tissues — kidney, skin, brain — and are also linked to cell movement 🏃‍♀️ and cancer metastasis 🧬.
• Especially AQP5, which is often overexpressed in cancer and linked to poor prognosis.

🧩 The Question

💭 “Do aquaporins (especially AQP5) influence how strongly cells stick together?”

Researchers tested this in MDCK cells (Madin-Darby canine kidney epithelial cells), a standard model for epithelial biology. They compared AQP1, AQP3, AQP4, and AQP5.

⚗️ Methods in a Nutshell

They used:

• 🧬 Genetic constructs: MDCK cells expressing EGFP-tagged AQPs.
• 🔬 Live imaging (time-lapse) for migration (wound-healing assay).
• 🧪 Dispase assay to test how easily cells detach.
• 💡 Immunostaining + confocal microscopy to visualize junctional proteins (β-catenin, γ-catenin, ZO-1, etc.).
• 🧠 FISH and western blotting to check mRNA/protein levels.
• 👩‍⚕️ Breast cancer tissues to see if the same happens in real tumors.

🚶‍♀️ Results Part 1 — AQP5 makes cells less sticky and more detached

• Overexpressing AQP5 caused cells to detach and scatter from the migrating layer instead of moving together. ➜ The sheet’s migration was 65% slower than control.
• Cells lost coordination between “leader” and “follower” cells.
• AQP5 overexpression made cell–cell junctions weaker, as shown by:
  • Reduced β-catenin, γ-catenin, ZO-1, and p120-catenin at the membrane.
  • More fragments in the dispase assay → weaker adhesion.
• But this did not trigger EMT (no increase in vimentin).

🧩 Mutation test:

• AQP5S156A (mutation blocking Ras signaling) partly rescued coordination → Ras pathway is key for detachment!

🧫 Results Part 2 — Effects on 3D cysts (mini-organoids)

In 3D cultures:

• Normal cells form nice hollow cysts (organized, like mini kidneys).
• AQP5-expressing cells formed cysts filled with cells, losing polarity. ➜ Looked more tumor-like.
• This shows AQP5 disrupts normal epithelial organization.

💗 Results Part 3 — Validation in human breast cancer

In tumor samples:

• High AQP5 ↔ Low γ-catenin (weaker adhesion).
• But no correlation with ZO-1. This supports the idea that AQP5 overexpression weakens cell junctions and could promote metastasis.

🔄 Results Part 4 — Other AQPs act differently

• AQP1 and AQP4: Also decreased junctional proteins.
• AQP3: Did the opposite — it increased β-catenin and made cells slightly more adhesive. ➜ Shows that different AQPs have different effects on adhesion.

🧬 Chimeric AQPs — Finding the “sticky” part

They swapped AQP3 and AQP5 cytoplasmic domains:

• Swapping loop D or the C-terminal tail of AQP5 into AQP3 reduced its “sticky” effect.
• Thus, those AQP5 regions are key for controlling adhesion.
• These effects are separate from water transport — they come from protein–protein signaling interactions.

💡 Final Insights

AQPs aren’t just water channels — they also:

• ⚖️ Control how tightly epithelial cells stick together.
• 🔁 Interact with signaling pathways (like Ras).
• 🧱 Affect morphogenesis and cancer progression.

👉 AQP5, AQP1, and AQP4 loosen cell junctions and may promote cancer spread, while AQP3 can strengthen junctions — showing dual, isoform-specific roles.

📚 Big Takeaway

Aquaporins act as “plumbing and glue” regulators — they balance water flow and the cell’s ability to hold its neighbors. In cancer, overexpression (especially of AQP5) may shift this balance toward cell detachment and metastasis.