PROSER2

Model summary

A human cytoskeletal adaptor that uses multivalent protein binding to organize actin-regulatory assemblies. By concentrating filament-nucleating and -elongating factors at membrane-proximal cortical sites, it enhances actin filament growth and stabilizes pseudopodial protrusions, thereby shaping cell morphology. It operates primarily in the cytosol and at the plasma membrane interface and can be packaged into extracellular vesicles, consistent with a trafficking-and-assembly cycle that tunes protrusion dynamics and cell shape.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The sequence carries a single annotated module: GO:0005515 protein binding. The absence of catalytic InterPro signatures and the presence of a generic protein-binding annotation indicate a non-enzymatic scaffold/adaptor whose primary role is to organize other proteins. Such adaptors often tune cytoskeletal dynamics by docking to actin regulators and membrane-associated complexes.

2. 02

   From this binding-centric core, I infer molecular function first.

   A scaffold that lacks catalytic motifs but is optimized for multivalent contacts causally supports GO:0005515 protein binding as the operative activity. This binding capacity provides the mechanistic basis for downstream cytoskeletal control.

3. 03

   The biological processes follow directly from how a binding scaffold modulates actin assemblies.

   Positive control of filament formation is captured by GO:0030838 positive regulation of actin filament polymerization. By stabilizing or recruiting nucleation/elongation factors at the cortex, the scaffold drives protrusive structures, aligning with GO:0031272 regulation of pseudopodium assembly. These protrusive and cytoskeletal outputs reshape the cell, satisfying GO:0008360 regulation of cell shape. Together, these processes describe a coherent axis: binding-driven assembly → enhanced actin polymerization → pseudopod dynamics → morphological control.

4. 04

   Cellular localization resolves the spatial logic of this mechanism.

   The soluble nature of a binding scaffold and its cytoskeletal targets place it in GO:0005829 cytosol, where it can sample and organize actin-regulatory complexes. Transient association with cortical assemblies and membrane-proximal actin networks explains presence at GO:0005886 plasma membrane, where protrusions initiate. Its detection in GO:0070062 extracellular exosome is consistent with cortical-to-vesicular trafficking and packaging of cytoskeleton regulators into secreted vesicles. This triad of compartments—cytosol, membrane-proximal cortex, and exosomes—maps onto a trafficking-and-assembly cycle that seeds and sustains pseudopodia.

5. 05

   Mechanistically, I hypothesize that the protein functions as a cortical adaptor that binds multiple partners to bias actin assembly.

   By concentrating actin nucleators and elongation factors at membrane interfaces, it elevates filament growth and stabilizes pseudopodial protrusions. Likely partners include core actin machinery and membrane-cytoskeleton linkers: actin itself and its regulators (e.g., Arp2/3 complex and profilin), elongation factors (Ena/VASP), barbed-end modulators (capping protein), and membrane-associated scaffolds (ERM proteins). Packaging into exosomes may reflect a feedback route whereby extracellular vesicles deliver cytoskeletal regulators to remodel neighboring cells. This binding-driven, cortex-centered mechanism causally explains its role in actin polymerization, pseudopod assembly, and cell shape control across cytosol and plasma membrane interfaces.