Summary: PAINT IBA for nuclear activity propagated from the sHSP family node PTN000897708 (zebrafish and other vertebrate members as descendant evidence).

Reason: Vertebrate sHSPs enter the nucleus under stress and the target is within the clade; there is no direct C. elegans evidence for nuclear HSP-16.41. Retained as a plausible but non-core location (the hsp-16.2 review accepted the same IBA).

Summary: PAINT IBA for cytoplasm from node PTN000897708, with several C. elegans sHSPs as descendant evidence.

Reason: HSP-16 proteins are soluble cytoplasmic chaperones without targeting signals; immunohistochemistry detects stress-induced HSP16s in many tissues.

Summary: PAINT IBA for response to heat from node PTN000897708.

Reason: The hsp-16 genes are the archetypal heat-inducible genes of C. elegans: never constitutively expressed and strongly induced by heat via HSF-1 and heat shock elements in the shared intergenic promoters.

Summary: hsp16-lacZ reporter study showing strictly heat-shock-dependent expression of the hsp16 gene pairs, with tissue differences between pairs and no inducibility in germline or early embryo.

Reason: Foundational expression evidence for the heat inducibility that defines the hsp-16 genes.

Summary: Microarray study: hsp-16 genes are among the genes induced by tunicamycin in an xbp-1-dependent manner (Table I).

Reason: The induction is real but HSP-16.41 is a cytoplasmic sHSP; its induction during ER stress is a secondary output, not participation in an ER-lumenal folding response. Non-core.

Summary: Same microarray result: tunicamycin induction of hsp-16 transcripts is attenuated in xbp-1 mutants.

Reason: xbp-1 dependence places the expression change downstream of IRE-1/XBP-1, but the sHSP is an output of that response, not a component of the signalling pathway. Non-core.

Summary: PAINT IBA for protein refolding from node PTN000897708. HSP-16.41 is an ATP-independent holdase that sequesters unfolding polypeptides to prevent aggregation rather than catalyzing protein refolding itself.

Reason: sHSPs of the alpha-crystallin/HSP20 family (PANTHER:PTN000897708) do not catalyze protein refolding themselves; they bind unfolding intermediates ATP-independently to prevent irreversible aggregation and maintain them in a state from which the ATP-dependent HSP70 chaperone system subsequently refolds them. Although GO:0042026 (protein refolding) is a biological process term, sHSP holdase sequestration occurs during stress to prevent irreversible aggregation independently of whether the client's downstream fate is HSP70-mediated refolding or proteasomal/autophagic degradation, and sHSPs are neither subunits nor cofactors of the ATP-dependent HSP70/J-domain/NEF refolding reaction once substrate is released, so attributing the downstream protein refolding process (GO:0042026) to the upstream stress holdase conflates distinct proteostasis steps (go-ontology#30552). Marked as over-annotated, consistent with the sibling C. elegans hsp-16 and vertebrate sHSP/alpha-crystallin reviews.

Summary: Tenor & Aballay reported that the Toll-like receptor TOL-1 is required for correct expression of hsp-16.41 in the pharynx during infection with Salmonella enterica.

Reason: Expression-pattern evidence only: hsp-16.41 expression depends on TOL-1 in a pathogen context. This places it among infection-responsive genes, but the paper does not show that HSP-16.41 itself executes antibacterial defense. Retained as a non-core response annotation.

Summary: Curator ISS transfer of unfolded protein holdase activity from a characterized sHSP.

Reason: HSP-16.41 is an alpha-crystallin-domain sHSP and its close paralogue HSP-16.2 suppresses thermal aggregation of citrate synthase in vitro, so ATP-independent holdase activity is well supported. However GO:0140309 retains a carrier definition (escort to an acceptor molecule or location), which has not been shown. Following the hsp-16.2 review and go-ontology#30552, the replacement is the proposed holdase chaperone activity NTR.

Proposed replacements: holdase chaperone activity