CXCR4 recognizes CXCL12 and couples ligand recognition to G-protein signaling and directed cell migration. The historical human-receptor activation study and the newer CXCL12–CXCR4–Gi report support the principal signaling unit (PMID:8752281(https://pubmed.ncbi.nlm.nih.gov/8752281/), PMID:39093700(https://pubmed.ncbi.nlm.nih.gov/39093700/)). Those two sources were inspected at abstract/summary level; unseen structural construct details are not inferred. Directly inspected trafficking and chemotaxis experiments provide additional support (PMID:19106094(https://pmc.ncbi.nlm.nih.gov/articles/PMC2645827/), PMID:21540189(https://pmc.ncbi.nlm.nih.gov/articles/PMC3121390/)). The compact source guide gives actual read scopes and public locators.
Ligand binding and receptor activation are distinct. The vMIP-II structure establishes binding of a viral CC chemokine antagonist to an engineered disulfide-trapped CXCR4 complex (PMID:25612609(https://pmc.ncbi.nlm.nih.gov/articles/PMC4362693/)). It does not establish CC-triggered transmembrane signaling. The real PAINT ancestor PTN001628461 includes the CXCR4 daughter, but the broader CC-receptor assertion exceeds this target's established ligand-class signaling evidence. The retained CC-binding observations are positive; no universal claim that all CC ligands are inactive is made. The inactive human CC-chemokine statement in the 1996 abstract concerns its HIV-inhibition experiment.
MIF signaling uses a CXCR4–CD74 receptor context. Actual co-immunoprecipitation and blocking experiments distinguish this from CXCL12 signaling, including the engineered CD74 retention-signal deletion used in surface experiments (PMID:19665027(https://pmc.ncbi.nlm.nih.gov/articles/PMC2911026/)). Extracellular ubiquitin recognition is likewise distinct from intracellular ubiquitination of the receptor (PMID:20228059(https://pubmed.ncbi.nlm.nih.gov/20228059/)). HIV coreceptor function remains a genuine contextual role. Herpesvirus-induced downregulation is not herpesvirus entry through CXCR4, and manipulation of CD28 does not establish a CXCR4 T-cell costimulator activity. The newer viral complex work resolved HIV-2 gp120 assemblies; HIV-1 high-resolution geometry was modeled (PMID:41027939(https://pubmed.ncbi.nlm.nih.gov/41027939/)).
The official 352-aa P61073-1 and 356-aa P61073-2 products independently reconstruct from VSP_001890 and both official FASTAs. P30991 identifiers are legacy aliases. The longer product replaces the first five residues with a nine-residue N terminus. The 1999 abstract reports calcium and chemotactic responses of human CXCR4-LO in a rat basophil leukemia host (PMID:10452968(https://pubmed.ncbi.nlm.nih.gov/10452968/)).
The 2023 paper's variant names differ from official isoform numbering: its variant 2 is the canonical 352-aa receptor, whereas variant 1 has the longer N terminus. Native-context leaky initiation and engineered initiation contexts can change the protein expressed. Tags, expression abundance and engineered G-alpha-qi calcium readouts also limit interpretation (PMID:37141381(https://pmc.ncbi.nlm.nih.gov/articles/PMC10159351/)). The two official product identities remain unchanged; equal behavior across products, extra official isoforms and native Gq coupling are not inferred.
Interactions were assessed individually from the actual cited sources, literal partner identities and raw records. Missing current IntAct pairs are not negative experiments. Positive associations with arrestins, USP14, receptor partners, myosin and drebrin support informative binding classes without giving CXCR4 its partner's catalytic or motor activity. ROGID identity establishes the sequence backbone, while tags, mutations and fragments remain separate experimental facts.
The myosin original identifies actin and MYH9 in tail pull-downs and reports endogenous myosin light-chain co-immunoprecipitation in human T cells; it does not purify every binary pair (PMID:12421915(https://pubmed.ncbi.nlm.nih.gov/12421915/)). Drebrin experiments distinguish endogenous human protein from rat drebrin-A constructs and directly follow CXCR4 recruitment to immunological synapses (PMID:20215400(https://doi.org/10.1242/jcs.064238), PMID:23926103(https://pmc.ncbi.nlm.nih.gov/articles/PMC3784756/)). USP14 tail pull-downs use cell lysates, whereas the original AIP4 Figure 1 caption explicitly describes purified His-AIP4/GST-tail binding (PMID:19106094(https://pmc.ncbi.nlm.nih.gov/articles/PMC2645827/), PMID:19116316(https://pubmed.ncbi.nlm.nih.gov/19116316/)).
The GPCR/RAMP screen is a suspension bead-array assay of membrane preparations. Its actual CXCR4 target entries in Tables S6 and S7 support RAMP3 association. The workbook initially declares A1 dimensions; complete extraction, after resetting dimensions, recovers the target rows. This is not yeast two-hybrid or proof of a native physiological complex (PMID:39083597(https://pmc.ncbi.nlm.nih.gov/articles/PMC11290489/)). The RNF113A paper's 2019 correction replaces a duplicated Figure 4A beta-actin control and states that conclusions are unchanged; it does not withdraw Figure 3 binding evidence.
Cellular-component observations remain valid even when a receptor activity is not demonstrated in that particular compartment. Actual HA-CXCR4 controls in the GPER trafficking paper establish surface labeling and delivery to EEA-1, Rab7 and LAMP-1 compartments. The title's emphasis on GPER does not invalidate these CXCR4 controls. CXCR4 is an input/substrate of ubiquitination and degradation machinery; the associated enzymes perform those reactions. Both inspected GO-CAM models give CXCR4 the CXCL12 receptor activity, consistent with the single compact signaling core.
The hypoxia source reports CXCR4 transcript induction; a response term can include expression changes without intrinsic oxygen sensing. The endothelial apoptosis source uses HIV envelope and a CXCR4-blocking antibody versus IgG, supporting a contextual receptor contribution rather than a general death-execution function. The specific CXCR4 adhesion intervention in PMID:19703720 remains unverified.
The mouse and rat donor studies support developmental and repair-related receptor functions. Mouse cuprizone experiments establish oligodendrocyte maturation and remyelination, but do not separately settle preservation of mature myelin (PMID:20534485(https://pmc.ncbi.nlm.nih.gov/articles/PMC2890706/)). Mouse adipose deletion and cold exposure support contextual thermogenic regulation while leaving the route to UCP1 unresolved; oxygen-consumption differences depend on normalization (PMID:25016030(https://pmc.ncbi.nlm.nih.gov/articles/PMC4202106/)). These sources do not establish human isoform-specific responses. Mouse dentate positioning and rat neurogenesis evidence were also checked against the actual donor contexts (PMID:12183377(https://pubmed.ncbi.nlm.nih.gov/12183377/), PMID:18434527(https://pubmed.ncbi.nlm.nih.gov/18434527/)).
The B-cell exosome study's exact target entry was not recovered. Failed supplemental access does not establish absence and no extracellular activity requirement is imposed on its location term. The hepatocellular-carcinoma vasculogenic-mimicry source likewise leaves the exact scope of the broad developmental assertion unresolved (PMID:20458337(https://pubmed.ncbi.nlm.nih.gov/20458337/), PMID:27693460(https://pubmed.ncbi.nlm.nih.gov/27693460/)). These uncertainties are retained without alleging gene misattribution.
The genuine fetch produced 117 source assertions from 118 raw records. One identical MYH9-binding source identity was collapsed by the ordinary seeder; both raw records remain in the TSV. Every source object, qualifier, partner and official product is preserved. Existing selected source caches are unchanged; supplemental publication caches came from the ordinary workflow. Falcon authentication and the configured Perplexity-lite quota failure are preserved as failures; no manual text is labeled as a provider report.
The primary core, donor, trafficking and context consultations were independently prepared by ROOT and read before integration. The former 17-row binding consultation was explicitly reassigned to this owner after the other agent remained unavailable; its completion is owner work, not independent peer review. Saved read ledgers distinguish complete abstracts, selected original text, figure captions, inaccessible originals and uninspected pixels/supplements. Initial informal access misstatements were corrected against the actual files: PMID:21540189 is full HTML, whereas PMID:25016030 is abstract-only in the normal cache with separate original-text recovery.
The source guide summarizes the actual 1,007-node family tree, target alignment, on-path IBDs, donor joins, three matching ARBA rules, interaction records and selected Reactome paths. The Oct 12 PAINT GAF is an authenticated historical capture, not a fresh Oct 15 download. HPA supplies predicted membrane/expression information but no inspected subcellular microscopy element. Raw evidence and intermediate failures remain in the immutable research packet; the public guide contains usable source locators instead of bulk dumps. Ordinary validation/status/render outcomes will be recorded separately once completed; this scientific draft does not claim a validation-derived final status.
CXCR4 converts extracellular CXCL12 gradients into a cellular migration signal. The original ligand-identification study and the active CXCL12–CXCR4–Gi structural report support receptor identity and coupling. An independently recovered functional study measures reduced cAMP after SDF-1alpha and inhibition of that response by AMD3100. Thus the ligand-specific pathway and the inhibitory G-protein branch describe complementary aspects of the same receptor unit; CXCR4 is upstream of the cyclase, rather than a cyclase enzyme itself [PMID:8752281; PMID:39093700; PMID:20228059, Methods and Figure 7/Results].
The axis also contributes to hematopoietic cell homing, discussed in the MIF/CD74 original. The preserved official UniProt record links pathogenic CXCR4 variants to WHIM syndrome and describes abundant mature myeloid cells in marrow despite peripheral neutropenia. These physiological and disease facts improve the standalone summary without adding a new developmental or disease-process annotation [PMID:19665027, Introduction/Discussion; genes/human/CXCR4/CXCR4-uniprot.txt, DISEASE: WHIMS1]. A separate claim about a specific hematopoietic progenitor retention assay is not manufactured from those descriptions.
Ligand binding, receptor-complex association and signaling are distinct measurements. Viral vMIP-II binds CXCR4 but is antagonistic; its engineered disulfide-trapped structure is not an agonist experiment. MIF-dependent AKT signaling requires CXCR4/CD74 in the tested human cells, and receptor co-immunoprecipitation supports the complex. The 2009 study cites earlier direct MIF-binding work rather than independently measuring that contact. The most specific directly inspected ligand class is therefore CXC chemokine binding, while positive MIF complex biology remains intact [PMID:25612609; PMID:19665027].
The intracellular tail connects CXCR4 to regulatory and cytoskeletal proteins. Actin was identified after receptor-tail pull-down, and myosin light chain co-precipitated with endogenous receptor. These observations support the existing contextual binding assertions; the precise binary interfaces remain unresolved. The relevant original text is available at https://www.researchgate.net/publication/11044228_Cutting_Edge_Association_of_the_Motor_Protein_Nonmuscle_Myosin_Heavy_Chain-IIA_with_the_C_Terminus_of_the_Chemokine_Receptor_CXCR4_in_T_Lymphocytes (GST pull-down Methods; Results and Figure 2 caption). The failed PDF request is not represented as full-PDF access PMID:12421915.
RAMP3 has a positive target result in the original membrane-capture screen, including the independently inspected Tables S6/S7. This is useful association evidence, but it does not identify a particular RAMP-dependent transport or signaling activity of CXCR4. The standing project instruction retains such supported generic interactions as non-core; the review's request to remove the positive assertion solely because it is generic is not adopted [PMID:39083597, Tables S6/S7].
Antigen-dependent CXCR4 recruitment occurs at the immunological synapse. The explicit UniProt location note traces the electronic junction mapping to that same experiment, so both source tuples now use the specific location. A receptor need not perform structural adhesion to be located there PMID:20215400. Conversely, the dendritic-cell source is a review whose accessible abstract discusses CCR7. Its full discussion and underlying CXCR4-specific evidence remain unverified, so that assertion is now undecided; the general CXCL12 ligand paper does not independently establish a dendritic-cell endpoint PMID:16621978.
Several remaining uncertainties are about experimental scope rather than absence of biology. Repair-associated OPC differentiation and remyelination do not separately demonstrate preservation of mature myelin. The exosome source requires a verified target-level detection, not receptor activity inside vesicles. The adhesion abstract separates pertussis-toxin sensitivity from chemokine-induced migration, and tumor vasculogenic mimicry does not automatically establish normal vasculature development. Short source-exact anchors now expose several of these boundaries; the quotes are confined to the review YAML and counted cumulatively [PMID:20534485; PMID:20458337; PMID:19703720; PMID:27693460].
This follow-up preserves every original annotation source object, both official products, all old note bytes and the prior append-only history record. The source guide records the clarified access limits and ontology specificity. The old history record is not rewritten to repair spacing; ROOT will create a new accurately spaced session record. No source cache or provider output was replaced, and no NEW annotation is proposed.