A tunable LIC1-adaptor interaction modulates dynein activity in a cargo-specific manner

Area of Science:

• Cell Biology
• Molecular Motors
• Protein-Protein Interactions

Background:

• Cytoplasmic dynein-1 is essential for retrograde transport of cellular components along microtubules.
• Activating adaptors link dynein to cargoes and dynactin, but their regulatory mechanisms are unclear.
• Understanding these adaptors is key to deciphering dynein-mediated transport.

Purpose of the Study:

• To elucidate the interaction mechanism between three distinct adaptor families and dynein.
• To investigate how adaptors regulate dynein's motor activity.
• To provide structural and functional insights into dynein-cargo complex formation.

Main Methods:

• X-ray crystallography to determine structural basis of interaction.
• Quantitative binding assays to measure affinities.
• In vitro motility assays to assess functional impact on dynein.

Main Results:

• Three unrelated adaptor subfamilies (BICD2, CRACR2a, HOOK3) bind the same amphipathic helix on dynein light intermediate chain-1 (LIC1).
• The hydrophobic interaction is conserved, but adaptors utilize distinct protein folds and surface contacts.
• Binding affinities varied between 1.5 and 15.0 μM, indicating differential interaction strengths.

Conclusions:

• A conserved hydrophobic interaction site on LIC1 accommodates diverse adaptor structures.
• Tunable binding affinities suggest a mechanism for cargo-specific regulation of dynein motility.
• This study reveals a fundamental principle in how dynein's function is modulated by its adaptors.