| Category | Key points (1-2 bullets) | Representative sources (first author year, journal) | URL (if available) |
|---|---|---|---|
| Identity/Structure | • Rat **Sstr5** matches UniProt **P30938**: somatostatin receptor type 5, a **class A/rhodopsin-like 7-transmembrane GPCR** in the somatostatin receptor family. • Canonically couples to **Gi/Go**, consistent with inhibition of adenylyl cyclase/cAMP signaling. (pqac-00000001, pqac-00000005, pqac-00000006) | Periferakis 2024, *Current Issues in Molecular Biology*; Yue 2012; Kasprzak 2021, *Biomedicines* | https://doi.org/10.3390/cimb46090578; https://doi.org/10.3390/biomedicines9111743 |
| Ligands/Pharmacology | • SSTR5 binds both SST peptides, with **~10-fold higher affinity for SST-28 than SST-14**. • **Octreotide** shows high affinity for **SSTR2/SSTR5**; **pasireotide** shows the **highest affinity for SSTR5** among common clinical analogs. (pqac-00000010, pqac-00000011, pqac-00000023, pqac-00000031) | Kasprzak 2021, *Biomedicines*; Milewska-Kranc 2023, *Cancers*; Tamura 2023, *Pharmacology Research & Perspectives* | https://doi.org/10.3390/biomedicines9111743; https://doi.org/10.3390/cancers16010116; https://doi.org/10.1002/prp2.1043 |
| Signaling | • Main signaling is **Gi/Go-mediated inhibition of adenylyl cyclase**, lowering intracellular **cAMP** and often **Ca2+**. • Additional reported outputs include modulation of **K+/Ca2+ channels**, activation of **protein tyrosine phosphatases**, and engagement of **PLC/MAPK** pathways. (pqac-00000000, pqac-00000009, pqac-00000012, pqac-00000013, pqac-00000014) | Farb 2017, *Endocrinology*; Periferakis 2024, *Current Issues in Molecular Biology*; Milewska-Kranc 2023, *Cancers* | https://doi.org/10.1210/en.2017-00639; https://doi.org/10.3390/cimb46090578; https://doi.org/10.3390/cancers16010116 |
| Expression/Localization | • Rat-relevant evidence indicates SSTR5 is expressed in **pituitary** and **pancreatic islets**; in rodents, **β-cells** are described as more exclusively expressing SSTR5, while rat **δ-cells** also show predominant SSTR5 expression in some studies. • Brain SSTR5 expression is reported as **higher in rats than humans**; broader tissue distribution includes CNS, pancreas, and GI tract. (pqac-00000008, pqac-00000013) | Yue 2012; Periferakis 2024, *Current Issues in Molecular Biology* | https://doi.org/10.3390/cimb46090578 |
| Recent 2023-2024 advances | • **Cryo-EM structures** of agonist-bound **SSTR5-Gi** complexes (CST17 and octreotide) resolved the orthosteric pocket, extracellular loop contributions, and a TM3/TM6 **“hydrophobic lock”** linked to activation. • 2024 work also reinforced SSTR5 as a therapeutic design target for more selective agonists. (pqac-00000015, pqac-00000016, pqac-00000017, pqac-00000024) | Li 2024, *PNAS* | https://doi.org/10.1073/pnas.2321710121 |
| Applications/Clinical | • SSTR5 is relevant to **somatostatin analog therapy** in endocrine/neuroendocrine disease because octreotide and especially pasireotide engage this subtype. • Real-world implementations include **oral octreotide** for acromegaly, **pasireotide** trials, and **radiolabeled octreotide PET** for somatostatin receptor imaging in NETs. (pqac-00000027, pqac-00000029, pqac-00000030, pqac-00000026, pqac-00000028, pqac-00000032) | ClinicalTrials.gov NCT03252353; NCT01895296; NCT00813592; NCT04552847; NCT03883776; Kasprzak 2021, *Biomedicines* | https://clinicaltrials.gov/study/NCT03252353; https://clinicaltrials.gov/study/NCT01895296; https://clinicaltrials.gov/study/NCT00813592; https://clinicaltrials.gov/study/NCT04552847; https://clinicaltrials.gov/study/NCT03883776; https://doi.org/10.3390/biomedicines9111743 |
| Quantitative data | • Selective SSTR5 antagonist **compound-1**: **IC50 9.8 nM (human)** and **31 nM (mouse)**, with **>1000-fold selectivity** over SSTR1-4 in reported profiling. • In HFD-fed mice, SSTR5 deletion lowered fasting glucose (**228.3 ± 70.6 vs 190.2 ± 30.1 mg/dL**), insulin (**87.5 ± 95.3 vs 32.5 ± 47.8 ng/mL**), and GHb (**4.8 ± 0.7% vs 4.0 ± 0.4%**); SSTR5 cryo-EM structures were solved at **2.7 Å and 2.9 Å**. (pqac-00000020, pqac-00000021, pqac-00000017) | Tamura 2023, *Pharmacology Research & Perspectives*; Li 2024, *PNAS* | https://doi.org/10.1002/prp2.1043; https://doi.org/10.1073/pnas.2321710121 |


*Table: This table summarizes the core functional annotation of rat Sstr5 (UniProt P30938), including identity, ligands, signaling, localization, recent advances, clinical relevance, and quantitative findings. It is useful as a compact evidence-backed reference for the receptor’s biology and translational significance.*