MAPKBP1

MAPKBP1 is a JNK-pathway scaffold protein that links JNK signaling to centriolar/basal-body biology and to the regulation of primary cilia, and whose disruption causes a cilia-independent form of nephronophthisis (NPHP20) (PMID:28089251, PMID:40814602). It dimerizes through a C-terminal loop-helix/coiled-coil domain that is necessary and sufficient for homodimerization and also mediates heterodimerization with its paralog WDR62 (PMID:23341463); truncation of this C-terminal region abolishes both dimerization and microtubule binding and severely reduces cell-cycle-dependent recruitment to centriolar structures (PMID:32505465). Wild-type MAPKBP1 associates with centrosomes, basal bodies, and microtubules and is recruited to mitotic spindle poles where it colocalizes with WDR62 (PMID:28089251, PMID:32505465), while endogenous MAPKBP1 also localizes to ciliary basal bodies in a manner controlled by JNK activation status: JNK activation drives MAPKBP1 dissociation from the basal body and concomitant cilia disassembly, placing MAPKBP1 upstream of JNK/actin-mediated control of ciliary length (PMID:40814602). Disease-causing mutations compromise spindle-pole recruitment and JNK2/WDR62 interactions, and loss of MAPKBP1 produces shortened primary cilia and elevated DNA damage response signaling without overt ciliogenesis defects in patient fibroblasts (PMID:28089251, PMID:40814602). MAPKBP1 protein abundance is itself a regulated node: METTL8 binds Mapkbp1 mRNA and represses its translation to suppress JNK signaling (PMID:29706498).

1. 2013 Medium

   Established the structural basis of MAPKBP1 self-association by identifying a C-terminal dimerization domain mediating homodimerization and WDR62 heterodimerization, defining MAPKBP1 as a WDR62-family scaffold.

   Evidence Sequence conservation analysis, reciprocal co-immunoprecipitation, and immunofluorescence including arsenite stress-granule assay

   PMID:23341463

   Open questions at the time

   • No high-resolution structure of the dimerization interface
   • Functional role of stress-granule co-localization with WDR62 not defined
   • JNK-relevant consequences of dimerization not tested
2. 2017 High

   Connected MAPKBP1 to human disease by showing it is recruited to mitotic spindle poles with WDR62 and that patient mutations disrupt this recruitment and JNK2/WDR62 interactions, while demonstrating the disease mechanism is cilia-independent.

   Evidence Immunofluorescence, co-immunoprecipitation, patient fibroblast analysis, and siRNA knockdown in murine cell lines

   PMID:28089251

   Open questions at the time

   • Mechanism linking spindle-pole localization to nephronophthisis unclear
   • Cause of increased DNA damage signaling on knockdown not resolved
   • Did not reconcile cilia-independent claim with later basal-body findings
3. 2018 Medium

   Placed MAPKBP1 protein levels under upstream control by showing METTL8 binds its mRNA and represses translation to dampen JNK signaling, identifying a regulatory input governing pathway output.

   Evidence RNA immunoprecipitation, translational reporter assay, JNK activity measurement, and ESC differentiation assay

   PMID:29706498

   Open questions at the time

   • Mechanism of translational repression not defined at nucleotide level
   • Direct effect of MAPKBP1 protein on JNK activity not isolated
   • Relevance to centriolar/ciliary functions untested
4. 2020 High

   Defined the C-terminal coiled-coil domains as required for microtubule binding and cell-cycle-dependent centriolar/basal-body recruitment, linking the dimerization module to subcellular targeting and disease.

   Evidence Reciprocal co-immunoprecipitation, fluorescence microscopy, and patient-derived deletion constructs in HeLa and IMCD cells

   PMID:32505465

   Open questions at the time

   • Direct microtubule-binding region within the protein not mapped
   • How dimerization couples to centriolar recruitment mechanistically unknown
   • No dominant-negative interaction between mutant and wild-type
5. 2025 Medium

   Integrated MAPKBP1 into JNK-dependent ciliary length control, showing JNK activation status governs basal-body association via distinct domains and that MAPKBP1 acts upstream of actin-mediated ciliary regulation.

   Evidence Patient-variant overexpression, knockdown, immunofluorescence, and pharmacological JNK/actin manipulation with ciliary length readout

   PMID:40814602

   Open questions at the time

   • Single study, not independently replicated
   • Identity of the distinct domains mediating JNK-dependent association vs dissociation not fully resolved
   • Direct biochemical link between MAPKBP1 and actin regulation unestablished
6. 2025 Low

   Linked MAPKBP1 to the DNA-damage-induced apoptotic response, showing its suppression blunts X-ray-induced apoptosis downstream of uORF-bypass translational upregulation.

   Evidence Ribosome profiling, siRNA knockdown, and apoptosis assay after X-ray irradiation in HEK293T cells

   PMID:39755339

   Open questions at the time

   • Single-lab single knockdown assay without orthogonal validation
   • No pathway placement beyond MAPK signaling enrichment
   • Mechanistic connection to JNK scaffold function unclear

• How JNK activity, MAPKBP1 dimerization, microtubule/centriolar targeting, and DNA-damage signaling are mechanistically integrated into a single pathway driving nephronophthisis remains unresolved.
• No structural model of MAPKBP1 in complex with JNK2 or WDR62
• Direct kinase/substrate relationships in the scaffolded JNK module undefined
• Causal chain from MAPKBP1 loss to elevated DNA damage signaling unmapped