Protein CutA Undergoes an Unusual Transfer into the Secretory Pathway and Affects the Folding, Oligomerization, and Secretion of Acetylcholinesterase

Abstract

The mammalian protein CutA was first discovered in a search for the membrane anchor of mammalian brain acetylcholinesterase (AChE). It was co-purified with AChE, but it is distinct from the real transmembrane anchor protein, PRiMA. CutA is a ubiquitous trimeric protein, homologous to the bacterial CutA1 protein that belongs to an operon involved in resistance to divalent ions ("copper tolerance A"). The function of this protein in plants and animals is unknown, and several hypotheses concerning its subcellular localization have been proposed. We analyzed the expression and the subcellular localization of mouse CutA variants, starting at three in-frame ATG codons, in transfected COS cells. We show that CutA produces 20-kDa (H) and 15-kDa (L) components. The H component is transferred into the secretory pathway and secreted, without cleavage of a signal peptide, whereas the L component is mostly cytosolic. We show that expression of the longer CutA variant reduces the level of AChE, that this effect depends on the AChE C-terminal peptides, and probably results from misfolding. Surprisingly, CutA increased the secretion of a mutant possessing a KDEL motif at its C terminus; it also increased the formation of AChE homotetramers. We found no evidence for a direct interaction between CutA and AChE. The longer CutA variant seems to affect the processing and trafficking of secretory proteins, whereas the shorter one may have a distinct function in the cytoplasm.

CutA Divalent Cation Tolerance Homolog (Escherichia coli) (CUTA) Regulates β-Cleavage of β-Amyloid Precursor Protein (APP) through Interacting with β-Site APP Cleaving Protein 1 (BACE1)

“…2), suggesting that methionine 63 may be a major initiation site for the L component of CUTA. Alternatively, it is possible that the L component of CUTA may also be derived through cleavage of the H component, as proposed previously (18,29). We also found that mutations of M43L and M63L did not completely abolish the generation of the L component (Fig.…”

“…It has previously been shown that mouse cuta variants are initiated at three in-frame ATG codons, and their encoded proteins can be separated as heavy and light components by SDS-PAGE (18).…”

“…Although it was later determined that CUTA does not directly interact with AChE and that the real membrane anchor protein of AChE is PRiMA (17), mouse CUTA was recently found to affect the processing and trafficking of AChE (18). The CUTA protein forms trimers through a region of ϳ100 residues that is strongly conserved from bacteria to vertebrates.…”

Integrated analysis of clinical signs and literature data for the diagnosis and therapy of a previously undescribed 6p21.3 deletion syndrome

“…It was recently demonstrated that the mouse variants of CuTA affect the folding, oligomerization and secretion of acetylcholinesterase (AChE) into a catalytically active conformation, and several studies point to a role of AChE in the development of epilepsy. 8 The inferred disruption, in our patient, of the glutamate pathway prompted us to consider anticonvulsant drugs modulating this pathway as prime drugs for seizure control. Indeed, valproate (transiently) and topiramate (more persistently) had a remarkable effect on seizure control and led to a general improvement in the developmental and behavioural disorders.…”

“…Both SYNGAP1 and CuTA are likely involved in the secretory pathway in neurons. 7,8 HPHF1 belongs to the polycomb group of genes and it was recently reported as a key regulator of homeobox and developmental gene expression. 9 Because of the potential role of these genes in brain plasticity and organ morphogenesis, we hypothesize that their haploinsufficiency explains the clinical findings in our patient, allowing us to define a new contiguous gene syndrome.…”