Annotation inferences using phylogenetic trees

Electronic Gene Ontology annotations created by ARBA machine learning models

Cloning and developmental expression of a nuclear ubiquitin-conjugating enzyme (DmUbc9) that interacts with small heat shock proteins in Drosophila melanogaster.

DmUbc9 interacts with Hsp23 in yeast two-hybrid and co-immunoprecipitation assays.

"In a two hybrid screen designed to identify proteins that interact with small heat shock proteins (sHsps), a Drosophila melanogaster homologue of yeast and human ubc9 (Dmubc9) was found to interact with Drosophila Hsp23"

PMID:16313561

Cold hardening and transcriptional change in Drosophila melanogaster.

Hsp23 is among stress proteins differentially expressed during cold hardening treatment.

"Taken together, these assays suggest that stress proteins, including Hsp23, Hsp26, Hsp83 and Frost as well as membrane-associated proteins may contribute to the cold hardening response."

PMID:16572729

Differences in the chaperone-like activities of the four main small heat shock proteins of Drosophila melanogaster.

All four sHSPs have chaperone-like activity; Hsp23 requires 5-fold molar excess for equivalent efficiency.

"A 5 M excess of Hsp23 and Hsp26 was required to obtain the same efficiency with either citrate synthase or luciferase as substrate."
Approximately 30% of luciferase activity is recovered with Hsp23 in refolding assays.

"In an in vitro refolding assay with reticulocyte lysate, more than 50% of luciferase activity was recovered when heat denaturation was performed in the presence of Hsp22, 40% with Hsp27, and 30% with Hsp23 or Hsp26."

PMID:19401761

Distinct mechanisms underlying tolerance to intermittent and constant hypoxia in Drosophila melanogaster.

Hsp23 is upregulated during constant hypoxia; P-element lines show increased survival.

"Heat shock proteins up-regulation (specifically Hsp23 and Hsp70) led to a significant increase in adult survival (as compared to controls) of P-element lines during CH."

PMID:19715580

The small heat shock protein (sHSP) genes in the silkworm, Bombyx mori, and comparative analysis with other insect sHSP genes.

Comparative analysis identifies conserved alpha-crystallin domains across insect sHSPs.

"The sHSPs have an α-crystalling domain comprising about 100 amino acid residues, which is the conserved structure of all sHSP sequences [6-8]"

PMID:26705243

Specific protein homeostatic functions of small heat-shock proteins increase lifespan.

Hsp23 overexpression improves luciferase refolding in S2 cells; HSP70 dependence was tested separately on Hsp27 and CG14207.

"Consistent with in vitro data (Morrow et al., 2006), overexpression of the classical small HSPs (HSP23, HSP26, and HSP27) increased luciferase refolding (Fig"
All four classical sHSPs are highly heat-inducible.

"The four classical small HSPs (HSP22, HSP23, HSP26, and HSP27) were all highly induced after a heat shock (Fig"

PMID:32437379

Small heat shock proteins determine synapse number and neuronal activity during development.

Hsp23 and Hsp26 colocalize in the cytoplasm of CNS cells and physically interact.

"The data show that sHSP23 and sHSP26 localize in the cytoplasm of CNS cells, in particular in the optic lobes and the central nerve cord (Fig 2A and 2B`)"
Hsp23 and Hsp26 modulate synapse number during development.

"we suggest that sHSP23 and sHSP26 together form a complex that promotes synapse formation in presynaptic neurons, Pkm is an anti-synaptogenic element in neurons through, but not restricted to, the modulation of sHsp23 and sHsp26 (Fig 5C)."

PMID:38944040

Next-generation Drosophila protein interactome map and its functional implications.

DPIM2 provides a broad affinity-purification/MS interaction resource; the quoted abstract describes network scale, while the Hsp23-Hsp26 pair is independently verified by PMID:32437379.

"The network contains 32,668 interactions among 3,644 proteins, organized into 632 clusters representing putative functional modules"

file:DROME/Hsp23/Hsp23-deep-research-falcon.md

Falcon deep research report on Hsp23 (Drosophila melanogaster)

Hsp23 is a cytosolic small heat shock protein (HSP20/sHSP family) of Drosophila melanogaster (CG4463; UniProt P02516) containing the conserved alpha-crystallin domain, clustered with Hsp22, Hsp26 and Hsp27 at locus 67B; it is ~20.6 kDa and cytosolic.

"Hsp23 is one of the canonical sHSPs (clustered with other sHSP genes at cytological position **67B**) and is described as a ~**20.6 kDa** cytosolic protein"
As an sHSP, Hsp23 acts as an ATP-independent molecular chaperone (holdase) that prevents nonspecific protein aggregation, functioning within the proteostasis network.

"a key mechanistic distinction emphasized in Drosophila-focused reviews is that sHSPs can **prevent nonspecific protein aggregation in an ATP‑independent manner**"
The generated report cites syntheses proposing cytoskeletal binding and embryonic roles; these are leads, not independently verified target-binding assays in this re-review.

"multiple syntheses cite evidence that Hsp23 can **bind cytoskeletal elements** (including **actin and microtubules**) and has been linked to **embryo morphogenetic processes**"
Hsp23 is a cytoplasmic/cytosolic sHSP, in contrast to the mitochondrial Hsp22; in the nervous system it localizes to CNS cytoplasm and concentrates at NMJ synaptic boutons together with sHsp26.

"sHsp23 is observed in **CNS cytoplasm** and to **concentrate at NMJ synaptic boutons** together with sHsp26"
Hsp23 transcription is regulated by the canonical heat-shock response (HSF binds the Hsp23 promoter via heat shock elements after heat stress), by dFOXO during oxidative stress, and by ecdysone during development.

"heat shock factor (**HSF**) is reported to bind tightly to the **Hsp23 promoter** after heat stress via heat shock elements"
dFOXO directly targets multiple inducible sHSP promoters including Hsp23, placing Hsp23 at the intersection of oxidative stress and proteostasis regulation.

"A mechanistic study of oxidative-stress transcriptional control in Drosophila reports that **dFOXO directly targets multiple sHSP promoters including Hsp23**"
Muscle-specific Hsp23 overexpression protects flight muscle against heat-stress-induced degeneration with both cell-autonomous and cell-nonautonomous (neuron/glia) protection, whereas Hsp70 overexpression does not protect in the same paradigm.

"**Muscle-specific Hsp23 overexpression** protects flight muscle and also provides **cell-nonautonomous protection** of motor neurons and glia after heat stress, whereas **Hsp70 overexpression does not** protect in the same paradigm"
Hsp23 overexpression reorganizes ubiquitinated proteins into perinuclear ring-like puncta and preserves the microtubule cytoskeleton after heat shock, linking Hsp23 to stress-resilient proteostasis and cytoskeletal integrity.

"Hsp23 overexpression is associated with **organized perinuclear ubiquitin puncta** and preservation of the **microtubule cytoskeleton** following heat shock"
Full PMID:32437379 reports reduced synapse number after Hsp23 overexpression alone and no significant change after its knockdown alone; joint Hsp23/Hsp26 overexpression has the opposite direction. These dosage-dependent outcomes do not demonstrate universal dispensability.

"In motor neurons, sHsp23 overexpression is reported to **reduce synapse number** (as quantified by active zones per NMJ) and is interpreted as **not required for synapse formation**"
Maternal loading/overexpression of Hsp23 in oocytes increases thermal tolerance of offspring embryos and improves larval performance, supporting a thermoprotective role during early development.

"developmental review evidence further indicates that **maternal loading/overexpression of Hsp23 in oocytes increases thermal tolerance of offspring embryos** and improves larval performance"

PMID:6801431

Immunofluorescence localization of a small heat shock protein (hsp 23) in salivary gland cells of Drosophila melanogaster.

file:DROME/Hsp23/Hsp23-notes.md

Hsp23 primary-source and full-gene re-review notes

PMID:3109982

Cellular localization of HSP23 during Drosophila development and following subsequent heat shock.

PMID:27483356

Small heat shock proteins mediate cell-autonomous and -nonautonomous protection in a Drosophila model for environmental-stress-induced degeneration.