NEK5

NEK5 is a NIMA-related kinase that governs centrosome integrity and the centrosome cycle: it localizes to the proximal ends of centrioles, and its kinase activity is required to maintain pericentriolar material and microtubule nucleation in interphase while preventing premature centrosome separation (PMID:25963817). On mitotic entry, NEK5 drives the timely loss of centrosome linker proteins to enable centrosome separation, bipolar spindle formation, and accurate chromosome segregation (PMID:25963817). Beyond the centrosome, NEK5 has a kinase-dependent mitochondrial function, interacting with the AAA+ protease LonP1 and with mitochondrial proteins (Cox11, MTX-2, BCLAF1) to control respiratory chain activity, ROS, mitochondrial mass, and mtDNA integrity after oxidative damage (PMID:25725288, PMID:33547867). NEK5 also contributes to genome stability through an interaction with Topoisomerase IIβ that forms after etoposide treatment, with NEK5 loss increasing double-strand breaks (PMID:31090963). In cell-cycle and proliferative contexts it binds Cyclin A2 and remodels cyclin levels to support proliferation (PMID:30675923), and in mouse oocyte meiosis it acts upstream of Wee1B to relieve inhibitory CDK1 phosphorylation and permit the G2/M transition (PMID:31304658). NEK5 is additionally a caspase-3 substrate whose cleavage promotes skeletal muscle differentiation (PMID:23727203).

1. 2013 Medium

   Established that NEK5 is regulated by proteolytic cleavage and links to a differentiation program, answering whether NEK5 has roles beyond cell division.

   Evidence In vitro caspase-3 cleavage assay with siRNA knockdown, overexpression, and myotube formation/caspase activity assays

   PMID:23727203

   Open questions at the time

   • Cleavage site and the catalytic state of the cleaved fragment not defined
   • Direct kinase substrates in the myogenic program unidentified
2. 2015 High

   Defined NEK5 as a centriole-proximal kinase required for centrosome integrity, resolving its core localization and function.

   Evidence Immunofluorescence localization, siRNA depletion, and kinase-inactive overexpression scoring centrosome components in human cells

   PMID:25963817

   Open questions at the time

   • Direct substrates at the centrosome not identified
   • How NEK5 restrains rootletin recruitment mechanistically unknown
3. 2015 High

   Showed NEK5 controls mitotic centrosome separation and spindle bipolarity, connecting interphase centrosome integrity to faithful chromosome segregation.

   Evidence siRNA depletion with live-cell imaging and immunofluorescence of centrosome linker and spindle markers

   PMID:25963817

   Open questions at the time

   • Phosphorylation targets driving linker dissolution not mapped
   • Regulatory relationship to other mitotic kinases unresolved
4. 2015 Medium

   Revealed an unexpected mitochondrial role, showing NEK5 kinase activity modulates respiratory chain output and ROS, broadening its functional scope.

   Evidence Yeast two-hybrid screen plus shRNA silencing, kinase-dead mutant, respiration and ROS assays

   PMID:25725288

   Open questions at the time

   • Whether Cox11/MTX-2/BCLAF1 are direct phosphorylation substrates not shown
   • Mechanism coupling NEK5 to complex IV activity undefined
5. 2019 Medium

   Connected NEK5 to the DNA damage response, showing it partners with TOPIIβ to limit double-strand break accumulation.

   Evidence Co-IP and proximity ligation assay for interaction dynamics with comet assay after etoposide and siRNA silencing

   PMID:31090963

   Open questions at the time

   • Whether NEK5 phosphorylates TOPIIβ not established
   • Step in the DDR pathway where NEK5 acts unclear
6. 2019 Medium

   Implicated NEK5 in proliferative control via Cyclin A2 binding and cyclin remodeling in cancer cells.

   Evidence Co-IP, western blot of cyclins, siRNA silencing, MTT assay and xenograft model in breast cancer

   PMID:30675923

   Open questions at the time

   • Single Co-IP without reciprocal validation
   • Direct vs indirect regulation of cyclin levels not distinguished
7. 2019 Medium

   Placed NEK5 in the meiotic G2/M switch upstream of Wee1B, defining a regulatory input controlling CDK1/MPF activation.

   Evidence siRNA depletion, localization, CDK1 phosphorylation western blot, MPF assay, and Wee1B co-depletion epistasis in mouse oocytes

   PMID:31304658

   Open questions at the time

   • Direct substrate linking NEK5 to Wee1B regulation unknown
   • Generalizability beyond mouse oocytes untested
8. 2021 Medium

   Extended the mitochondrial role by showing NEK5–LonP1 interaction supports mitochondrial mass and mtDNA integrity under oxidative stress.

   Evidence Co-IP, mitochondrial fractionation, kinase-dead mutant, mitochondrial mass/function and mtDNA integrity assays

   PMID:33547867

   Open questions at the time

   • Whether LonP1 or TFAM are NEK5 phosphosubstrates not shown
   • Direct evidence for the proposed LonP1-TFAM module incomplete
9. 2021 Low

   Linked NEK5 activity to cytoskeletal reorganization and cell migration independent of proliferation.

   Evidence Stable overexpression/shRNA lines, cytoskeletal immunofluorescence, transwell migration, and murine xenograft

   PMID:34196902

   Open questions at the time

   • No molecular mechanism for cytoskeletal regulation identified
   • Phenotype not tied to a defined substrate or pathway
10. 2022 Medium

    Defined a NEK5 proximity interactome and phosphoproteome, integrating its centrosomal, mitochondrial, cytoskeletal and signaling roles and adding Src-pathway regulation.

    Evidence BioID proximity labeling MS, global phosphoproteomics, Src signaling western blot, 3D Matrigel culture in breast epithelial cells

    PMID:36550548

    Open questions at the time

    • Direct substrates among phosphoproteome hits not validated
    • Which interactome members are bona fide substrates vs proximity neighbors unresolved

• The direct physiological substrates of NEK5 kinase activity remain unidentified across all its reported compartments and functions.
• No validated direct phosphosubstrate at the centrosome, mitochondria, or in the DDR
• Structural basis of substrate recognition unknown
• Regulation of NEK5 kinase activation not defined