CNPPD1

Model summary

A human cyclin-like adaptor that assembles and regulates kinase-centered signaling modules at the endoplasmic reticulum to coordinate cell division and ciliogenesis. By using a cyclin scaffold to bind and tune cyclin-dependent kinase pathways, it times and stabilizes cytokinetic events and promotes assembly of the primary cilium. Its ER residency positions it to couple membrane trafficking and cytoskeletal remodeling, providing a hub that integrates phosphorylation signals with the assembly of division and ciliary machinery.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture: a single, continuous cyclin-PHOSPHO-like module, IPR013922 (Cyclin PHO80-like family) spanning residues 24–318.

   This architecture defines a cyclin fold that creates a conserved hydrophobic interface for docking and activating cyclin-dependent kinases (CDKs). The absence of catalytic motifs and the presence of a cyclin scaffold dictate that the polypeptide functions primarily through regulated protein–protein interactions rather than enzymatic chemistry, directly supporting GO:0005515 protein binding as the molecular function. The cyclin-PHOSPHO lineage is classically used to assemble and tune CDK signaling modules that drive cell-cycle transitions and cytoskeletal remodeling.

2. 02

   From this cyclin-driven binding function, I infer two connected biological processes.

   First, cyclin-mediated CDK activation is a canonical route to control cell division mechanics; by modulating kinase targeting and timing, this architecture causally regulates the assembly and progression of the division machinery, aligning with GO:0032465 regulation of cytokinesis. Second, the same cyclin toolkit is repeatedly repurposed to coordinate membrane trafficking and cytoskeletal dynamics that underlie organelle biogenesis. The provided biological processes—GO:0032465 regulation of cytokinesis and GO:0060271 cilium assembly—are mechanistically coherent: both require tightly choreographed cytoskeletal and membrane events that are classically governed by cyclin–CDK modules and their adaptors.

3. 03

   Cellular localization further constrains mechanism.

   The protein is assigned to the endoplasmic reticulum (GO:0005783 endoplasmic reticulum). A cyclin scaffold at the ER indicates a role at ER–cytoskeleton and ER–cilium interfaces. ER-based platforms coordinate membrane supply and signaling cues essential for ciliogenesis and for the membrane–abscission steps of cytokinesis. Thus, ER residency provides the physical hub from which the cyclin module can couple CDK signaling to membrane and cytoskeletal pathways.

4. 04

   Putting these strands together yields a mechanistic hypothesis.

   The cyclin-PHOSPHO-like core (IPR013922, residues 24–318) forms a docking surface that recruits and modulates CDKs and accessory factors at the ER. This causes selective phosphorylation cascades that time cytokinetic ring assembly and membrane scission, and simultaneously prime pathways for ciliogenesis—likely by regulating trafficking of ciliary membrane proteins and microtubule-associated assemblies emerging from ER-associated export routes. The ER localization explains how the protein integrates signals and substrates to coordinate both division and cilium assembly.

5. 05

   I therefore expect the protein to act as an ER-tethered cyclin adaptor that binds CDKs and their regulators, assembling transient complexes that tune cytokinesis and ciliogenesis.

   Likely interaction partners include ER-associated CDKs and their inhibitors, cytoskeletal organizers, and vesicle-coat systems that traffic ciliary components and cytokinetic machinery.