COBLL1

COBLL1 is an actin-binding adaptor protein that operates as a context-dependent signaling scaffold across several cancer and developmental settings (PMID:29686105, PMID:35352878). In castration-resistant prostate cancer it localizes to the nucleus, where it binds the androgen receptor and promotes complex formation with CDK1 to facilitate AR phosphorylation and genomic binding, while driving a neuron-like cell morphology and increased growth and migration (PMID:29686105). In chronic myeloid leukemia COBLL1 confers tyrosine-kinase-inhibitor resistance through two converging mechanisms: it increases IKKγ protein stability to activate NF-κB and reduce nilotinib-induced apoptosis (PMID:28232743), and it binds PACSIN2 with higher affinity than SH3BP1, competitively displacing SH3BP1 to activate downstream Rac1 signaling and suppress TKI-mediated apoptosis (PMID:35352878). In chronic lymphocytic leukemia COBLL1 is a binding partner of the ROR1 receptor tyrosine kinase and modulates B-cell receptor signaling (enhanced PLCγ2 and SYK phosphorylation) while impairing chemotaxis and motility (PMID:29122990). COBLL1 transcription is epigenetically silenced by EBV EBNA3C, which recruits KDM2B to remove activating H3K4me3 and Polycomb proteins BMI1/SUZ12 to deposit repressive H3K27me3 at the locus (PMID:30135119). Loss-of-function in Xenopus and zebrafish causes craniofacial dysmorphologies, establishing a developmental role in palate formation (PMID:36493769).

1. 2017 Medium

   Linking COBLL1 to a defined drug-resistance pathway addressed how it influences leukemia cell survival; it was shown to stabilize IKKγ and activate NF-κB to blunt TKI-induced apoptosis.

   Evidence Overexpression/knockdown in CML cell lines with western blot for IKKγ and NF-κB readouts plus nilotinib apoptosis assays

   PMID:28232743

   Open questions at the time

   • Mechanism by which COBLL1 stabilizes IKKγ (direct binding vs. indirect) not defined
   • No structural basis for the interaction
2. 2017 Medium

   Identifying COBLL1 as a ROR1 partner placed it in receptor and B-cell receptor signaling, clarifying its role in CLL cell behavior including motility and antigen-receptor responsiveness.

   Evidence Protein interaction assay plus chemotaxis, motility, and phospho-flow/western readouts of PLCγ2 and SYK in CLL cells

   PMID:29122990

   Open questions at the time

   • Whether the ROR1 interaction is direct is not resolved
   • Connection between ROR1 binding and BCR signaling modulation not mechanistically traced
3. 2018 Medium

   Defining a nuclear COBLL1–AR–CDK1 complex answered how COBLL1 promotes prostate cancer progression, showing it facilitates AR phosphorylation and genomic binding.

   Evidence Reciprocal Co-IP of nuclear COBLL1 with AR and CDK1 plus knockdown with morphological, proliferation, and migration phenotypes in CRPC cells

   PMID:29686105

   Open questions at the time

   • Whether CDK1 directly phosphorylates AR within the complex not established
   • Mechanism of COBLL1 nuclear localization unknown
4. 2018 Medium

   Establishing how a viral oncoprotein controls COBLL1 expression revealed the locus is silenced epigenetically, identifying COBLL1 as an EBNA3C target.

   Evidence ChIP for H3K4me3/H3K27me3 and BMI1/SUZ12, Co-IP for EBNA3C-KDM2B, and recombinant virus with EBNA3C motif mutants

   PMID:30135119

   Open questions at the time

   • Functional consequence of COBLL1 silencing for EBV-transformed cells not defined
   • Whether EBNA3C binds the COBLL1 locus directly or via cofactors unclear
5. 2022 Medium

   Resolving the molecular basis of COBLL1-driven TKI resistance showed it acts as a competitive scaffold, sequestering PACSIN2 to release SH3BP1 and activate Rac1.

   Evidence Co-IP, competitive binding/pulldown affinity assays, and TKI apoptosis assays with Rac1 pathway readout in CML

   PMID:35352878

   Open questions at the time

   • Structural basis for differential PACSIN2 affinity not determined
   • Relationship between this Rac1 axis and the NF-κB mechanism not integrated
6. 2022 Medium

   Genetic loss-of-function in vertebrate models established a developmental requirement for COBLL1, linking it to craniofacial and palate formation.

   Evidence CRISPR-Cas9 knockout in Xenopus laevis and Danio rerio with craniofacial morphological readout

   PMID:36493769

   Open questions at the time

   • Molecular pathway underlying the craniofacial defect not identified
   • Relevance to human craniofacial disease not demonstrated in the corpus

• How COBLL1's distinct scaffolding activities (AR/CDK1, IKKγ, PACSIN2, ROR1) relate to a unified biochemical function, and how its actin-binding domain contributes mechanistically, remains unresolved.
• No structural model of COBLL1 or its domains in the corpus
• No unifying biochemical activity connecting its multiple partner interactions
• Phosphorylation regulation only computationally predicted [#6]