The formin mDia2 stabilizes microtubules independently of its actin nucleation activity

Area of Science:

• Cell Biology
• Molecular Biology

Background:

• Microtubule (MT) polarization is crucial for cell migration.
• The Rho/mDia pathway is involved in MT stabilization, but the exact mechanism is unclear.
• mDia proteins are known for actin nucleation, but their role in MT stabilization is less understood.

Purpose of the Study:

• To investigate whether mDia2's MT stabilization activity is linked to its actin nucleation function.
• To determine if mDia2 directly interacts with and stabilizes microtubules.
• To elucidate the novel MT stabilization mechanism of mDia2.

Main Methods:

• Generated constitutively active mDia2 mutants affecting actin binding (K853A, I704A) and dimerization (W630A).
• Assessed MT stabilization in cells expressing mDia2 mutants.
• Performed in vitro assays to examine direct mDia2 binding to and effects on MTs.

Main Results:

• Actin-binding and dimerization-impaired mDia2 mutants still induced MT stabilization and bound to MT TIP proteins (EB1, APC).
• Constitutively active FH1FH2mDia2 directly bound to microtubules in vitro.
• FH1FH2mDia2 stabilized MTs against disassembly and modulated MT growth and shortening dynamics.

Conclusions:

• mDia2 possesses a direct, novel MT stabilization activity independent of its actin nucleation function.
• This MT stabilization activity is crucial for MT polarization during cell migration.
• mDia2 represents a new target for understanding and potentially modulating cell migration.