| Claim (short) | Evidence/Details | System/Organism | Source (paper + year + DOI URL) | Context ID(s) |
|---|---|---|---|---|
| Family classification: soluble Class IIB PITP | RdgBβ is described as a **soluble class IIB phosphatidylinositol transfer protein** within the RdgB/PITP family, distinct from multidomain RdgBα/Class IIA proteins; Drosophila has an rdgBβ subfamily member and assignment is based on PITP-domain similarity. | Family-level annotation; Drosophila + mammalian comparison | Hsuan & Cockcroft 2001, Genome Biology, https://doi.org/10.1186/gb-2001-2-9-reviews3011; Cockcroft et al. 2016, Biochem Soc Trans, https://doi.org/10.1042/bst20150228 | (pqac-00000000, pqac-00000011) |
| Lipid ligands/specificity: PI/PA vs PC | Class II/RdgBβ proteins are reported to bind and transfer **PI and PA**, with **very little PC**; under PLC/PLD-stimulated conditions RdgBβ shifts toward greater PA binding, and PA transfer is described as robust relative to Class I PITPs. | Conserved RdgBβ/PITPNC1 family conclusion | Cockcroft & Garner 2013, Adv Biol Regul, https://doi.org/10.1016/j.jbior.2013.07.007; Cockcroft et al. 2016, Biochem Soc Trans, https://doi.org/10.1042/bst20150228 | (pqac-00000007, pqac-00000011) |
| 14-3-3 docking sites and stability control | Two phosphorylated serines in the disordered C-terminus (**Ser274 and Ser299**) form the 14-3-3 docking module; mutation of either site abolishes 14-3-3 binding. 14-3-3 shields nearby **PEST** sequences and stabilizes RdgBβ. | Human PITPNC1/RdgBβ experimental system; family-relevant inference | Garner et al. 2011, Biochem J, https://doi.org/10.1042/bj20110649 | (pqac-00000004, pqac-00000005, pqac-00000010, pqac-00000014) |
| Proteasome turnover / half-life | RdgBβ is **ubiquitinated** and degraded via the **proteasome**. Wild-type protein has an approximate **4 h half-life**, whereas a 14-3-3-binding-defective mutant is reduced to about **2 h**, indicating 14-3-3 binding protects against turnover. | Human PITPNC1/RdgBβ in cells | Garner et al. 2011, Biochem J, https://doi.org/10.1042/bj20110649 | (pqac-00000004, pqac-00000005, pqac-00000006, pqac-00000014) |
| ATRAP interaction and PKC/PMA dependence | The **PITP domain** of RdgBβ interacts with the integral membrane protein **ATRAP/AGTRAP** at a site distinct from the 14-3-3 site. Interaction and membrane recruitment increase after **PMA** treatment and are reduced by the PKC inhibitor **BIM**, supporting **PKC-dependent** regulation. | Human PITPNC1/RdgBβ; mechanistic family inference | Garner et al. 2011, Biochem J, https://doi.org/10.1042/bj20110649; Cockcroft & Garner 2013, Adv Biol Regul, https://doi.org/10.1016/j.jbior.2013.07.007 | (pqac-00000004, pqac-00000008, pqac-00000009, pqac-00000007, pqac-00000014) |
| Membrane recruitment fold change | Upon PMA treatment, wild-type RdgBβ shows about an **8-fold increase** in the membrane fraction, whereas a 14-3-3-binding-deficient mutant shows about a **14-fold increase**, indicating 14-3-3 restrains membrane translocation. | Human PITPNC1/RdgBβ in COS-7 cells | Garner et al. 2011, Biochem J, https://doi.org/10.1042/bj20110649 | (pqac-00000005, pqac-00000014) |
| Very low/undetectable in vitro PI transfer | RdgBβ is far weaker than canonical PITPα in PI transfer assays. Reported thresholds: PITPα active at **~200–500 ng/ml**, while RdgBβ requires **~10–100 μg/ml** for detectable/significant activity (roughly **100–250-fold less active** by concentration). Endogenous/overexpressed RdgBβ fractions typically show **no detectable PI transfer** under tested conditions. | Human PITPNC1/RdgBβ; rat heart cytosol | Garner et al. 2011, Biochem J, https://doi.org/10.1042/bj20110649; Cockcroft et al. 2016, Biochem Soc Trans, https://doi.org/10.1042/bst20150228 | (pqac-00000004, pqac-00000005, pqac-00000006, pqac-00000009, pqac-00000002, pqac-00000014) |
| Tissue enrichment / localization clue | RdgBβ is reported as enriched in **heart** (and also brain in review discussion); cytosolic activity peaks attributable to RdgBβ were not observed, leading to the proposal that it acts **locally at membranes/contact sites** after recruitment rather than as a bulk soluble transfer activity. | Rat heart / review interpretation | Cockcroft & Garner 2013, Adv Biol Regul, https://doi.org/10.1016/j.jbior.2013.07.007; Cockcroft et al. 2016, Biochem Soc Trans, https://doi.org/10.1042/bst20150228 | (pqac-00000001, pqac-00000002) |
| Distinction from RdgBα | RdgBβ is a **small soluble** PITP with a short disordered tail and protein-partner-mediated membrane recruitment, whereas **RdgBα** is a **multidomain** protein with FFAT/DDHD/LSN2-related modules that localizes to **ER–PM contact sites** via VAP. This distinction is important to avoid confusing Drosophila rdgBbeta with rdgB/rdgBα phototransduction literature. | Family comparison | Hsuan & Cockcroft 2001, Genome Biology, https://doi.org/10.1186/gb-2001-2-9-reviews3011; Cockcroft et al. 2016, Biochem Soc Trans, https://doi.org/10.1042/bst20150228 | (pqac-00000000, pqac-00000011) |
| Drosophila-specific C-terminus difference | The Drosophila rdgBβ isoform is explicitly noted to **lack the short carboxy-terminal extension** present in human RdgBβ. Thus, C-terminal regulatory findings from mammalian PITPNC1/RdgBβ (e.g., Ser274/Ser299 14-3-3 docking) should be transferred to **Drosophila CG17818/Q9U9P7 cautiously**. | Drosophila-specific annotation | Hsuan & Cockcroft 2001, Genome Biology, https://doi.org/10.1186/gb-2001-2-9-reviews3011 | (pqac-00000000) |


*Table: This table compiles experimentally supported properties of the RdgBβ/PITPNC1 family most relevant to annotating Drosophila rdgBbeta (CG17818; UniProt Q9U9P7). It highlights where evidence is direct versus family-based inference and flags the important Drosophila-specific C-terminal difference.*