DYNLT3

DYNLT3 is a cytoplasmic dynein light chain that confers cargo-binding specificity, coupling the dynein motor to distinct intracellular transport and signalling functions (PMID:17289665, PMID:33772156). It directly and exclusively binds the spindle checkpoint protein Bub3 — an interaction not shared by other dynein light chains — thereby linking cytoplasmic dynein to the spindle assembly checkpoint (PMID:17289665). Consistent with this role, DYNLT3 localizes to kinetochores at prometaphase and is depleted upon chromosome alignment, mirroring Bub3, and its loss elevates the mitotic index with accumulation in prophase/prometaphase, indicating a function in chromosome congression and the transport of checkpoint proteins from kinetochore to spindle pole (PMID:17289665). The same kinetochore role extends to meiosis, where DYNLT3 depletion in oocytes causes chromosome misalignment, kinetochore-microtubule detachment, and impaired homologous chromosome segregation (PMID:21693773). In a separate transport context, DYNLT3 is required in melanocytes for efficient melanosome transport, regulation of melanosome acidity, and transfer to keratinocytes (PMID:33772156). DYNLT3 also acts as a regulator of EMT and Wnt/β-catenin pathway proteins in cervical and breast cancer cells, where it suppresses proliferation, migration, and invasion (PMID:35965516, PMID:37260179).

1. 2007 High

   Established how cytoplasmic dynein is physically coupled to the spindle checkpoint by identifying DYNLT3 as the exclusive light-chain link to Bub3, and showed this link operates at kinetochores during mitosis.

   Evidence GST pull-down and reciprocal co-immunoprecipitation for binding; immunofluorescence localization and siRNA knockdown with mitotic-index quantification for function

   PMID:17289665

   Open questions at the time

   • Whether DYNLT3 physically tethers Bub3 to an intact dynein motor in a reconstituted system is not shown
   • The structural basis of Bub3 exclusivity for DYNLT3 over other light chains is undefined
   • Direct demonstration that DYNLT3-dependent dynein actively strips checkpoint proteins to the spindle pole is not provided
2. 2011 Medium

   Extended the kinetochore role of DYNLT3 from mitosis to meiosis, establishing its requirement for chromosome alignment and segregation in oocytes.

   Evidence Immunofluorescent localization and antibody-mediated depletion with chromosome-spread and spindle readouts in mouse oocytes

   PMID:21693773

   Open questions at the time

   • Whether the meiotic phenotype depends on the DYNLT3-Bub3 interaction was not tested
   • Single-lab, antibody-injection approach without genetic confirmation
3. 2021 Medium

   Defined a distinct cargo-transport role for DYNLT3 in melanocytes, linking it to melanosome positioning, acidity, and transfer, and connecting its expression to Wnt/β-catenin signalling.

   Evidence Live-cell motion analysis, pH measurements, and transfer assays in knockdown melanocytes; β-catenin modulation with Western blot of Dynlt3 levels

   PMID:33772156

   Open questions at the time

   • The β-catenin regulation of Dynlt3 rests on a single Western-blot readout without direct promoter or binding evidence
   • The identity of the melanosomal cargo adaptor engaged by DYNLT3 is unknown
   • Mechanism linking dynein-driven transport to melanosome acidity is not resolved
4. 2023 Medium

   Positioned DYNLT3 as a regulator of EMT and Wnt/β-catenin pathway proteins in cancer, where its level inversely controls proliferation, migration, and invasion.

   Evidence Knockdown and overexpression with Western blotting of pathway/EMT markers plus proliferation, migration, invasion, apoptosis assays and nude-mouse xenografts in cervical and breast cancer cells

   PMID:35965516 PMID:37260179

   Open questions at the time

   • Pathway placement rests on protein-level readouts without direct binding or reconstitution
   • How a dynein light chain mechanistically modulates Wnt components is undefined
   • Whether the cancer effects require dynein motor function or the Bub3 interaction is untested

• It remains unknown how a single dynein light chain mechanistically reconciles its kinetochore/checkpoint role, its melanosome transport role, and its modulation of Wnt/EMT signalling.
• No structural model of DYNLT3 within the dynein complex or with cargo adaptors
• No unifying biochemical mechanism linking the distinct cellular contexts
• Direct cargo specificity determinants beyond Bub3 are uncharacterized