BICDL1

Model summary

A cytoplasmic dynein-adaptor scaffold that assembles and stabilizes motor–cargo transport complexes to drive minus-end-directed trafficking of late endosomes and lysosomes toward the centrosomal region. By organizing dynein with accessory factors, it concentrates cargo near the microtubule-organizing center and perinuclear area, thereby promoting endosome maturation and delivery into the lysosomal pathway. Its soluble adaptor architecture supports broad protein interactions in the cytosol and transiently associates with membrane-derived vesicles near the cell periphery.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The polypeptide is dominated by IPR051149 (Spindly/BICDR Dynein Motor Adapter family, residues 24–554), a hallmark of dynein adaptor scaffolds that recruit and regulate cytoplasmic dynein for minus-end-directed transport along microtubules. Embedded near the C-terminus is IPR060493 (BICD family-like cargo adapter 1/2-like, C-terminal domain, residues 489–542). This C-terminal module typically forms a cargo/adaptor-binding platform that stabilizes complexes with dynein, LIS1, and dynactin, and it often dictates cargo specificity and pathway choice. The ordered layout—an extended dynein-adaptor core capped by a cargo/adaptor-binding C-terminal domain—creates a multivalent scaffold optimized for protein–protein interactions rather than catalysis, directly supporting GO:0005515 protein binding as the molecular function.

2. 02

   A dynein-adaptor scaffold causes directional vesicle and organelle transport toward microtubule minus ends concentrated at the centrosome and perinuclear region.

   Such transport is a prerequisite for endosome maturation and fusion pathways that culminate in lysosome biogenesis and delivery. By coupling cargo selection to dynein activation, this architecture drives endosome-to-lysosome progression, aligning with GO:0008333 endosome to lysosome transport. The same mechanism explains pericentrosomal accumulation of late endosomes and lysosomes and the observed perinuclear enrichment.

3. 03

   Cellular localization follows from this transport logic.

   A soluble adaptor that binds dynein and cargos operates in the cytoplasm and cytosol (GO:0005829 cytosol), where it assembles transport complexes. Minus-end-directed trafficking concentrates cargo at the microtubule-organizing center, consistent with GO:0005813 centrosome. Vesicle carriers derived from or destined for the cell surface traverse the periphery; adaptor-mediated sorting and retrieval rationalize transient association with the GO:0005886 plasma membrane. Together, these features place the protein in cytoplasmic and centrosomal territories with dynamic membrane-proximal excursions.

4. 04

   Mechanistically, the N-to-C adaptor framework recruits dynein and dynactin, stabilizes the motor–cargo ensemble, and biases movement toward centrosomes.

   This causes pericentrosomal clustering of late endosomes and lysosomes and supports their maturation. I hypothesize that the scaffold binds dynein heavy chain and intermediate chain to activate motility, engages LIS1 and dynactin to enhance processivity, and recognizes late endosomal/lysosomal determinants (potentially Rab7 and HOPS/CORVET-associated factors). Likely interaction partners therefore include cytoplasmic dynein components, LIS1, dynactin subunits, and late endosomal regulators that collectively steer vesicles through the endo-lysosomal pathway.