The structure and assembly of gp80 cell adhesion complexes in Dictyostelium
Bibliographic record
Abstract
Studies on the Dictyostelium adhesion molecule gp80 have revealed the association of gp80 with lipid rafts and the assembly process of raft-based adhesion complexes. Membrane rafts were isolated from Dictyostelium cells as both Triton X-100-insoluble membranes and plasma membrane fragments using a detergent-free method. Each complex contained gp138, DdCD36, gp80, actin and ponticulin. Similar to vertebrate rafts, many of the Dictyostelium raft proteins were acylated and the raft membrane fractions were enriched with sterols. The raft membranes shared properties with isolated Dictyostelium contact regions, suggesting that rafts function in gp80-mediated adhesion. Moreover, gp80 colocalized with raft proteins and lipids at cell-cell contacts and sterol sequestration inhibited gp80-mediated adhesion. To elucidate how gp80 adhesion complexes are assembled, gp80-gp80 and gp80-raft interactions were investigated. Chemical cross-linking experiments revealed that rafts were enriched with gp80 oligomers. For other glycosylphosphatidylinositol (GPI)-anchored proteins, lipid-lipid interactions between their anchors and the rafts can cluster the proteins. In contrast, gp80 oligomers resisted sterol sequestration, suggesting that, in addition to raft compartmentalization, other factors are involved. Indeed, gp80 oligomerization was mediated by direct gp80-gp80 interactions and gp80 existed predominantly as cis-oligomers. The enrichment of these species in the raft domains may facilitate the establishment of high avidity trans-interactions during the initial stage of adhesion complex assembly. In many adhesion complexes, receptors also form links to the cytoskeleton via cytoplasmic adaptor proteins. For the Dictyostelium contact regions, the raft component ponticulin was found to mediate interactions with the actin cytoskeleton. Intriguingly, gp80 and ponticulin appeared to interact indirectly through their mutual association with membrane rafts. Studies using gp80 and ponticulin null mutants suggested that gp80 was able to produce large, nascent, cytoskeleton-free adhesion complexes. gp80 also recruited ponticulin into rafts and to cell-cell contacts and was required for formation of the cytoskeleton-associated complexes. Thus, gp80-gp80 interactions might enlarge and stabilize associated rafts to recruit ponticulin and elevate raft-cytoskeleton interactions. A model is proposed for the assembly of GPI-anchored adhesion molecule complexes through reciprocal raft-receptor interactions: rafts facilitate initial receptor interactions that then enlarge and stabilize the rafts to induce signaling and cytoskeleton recruitment.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".