Complex alternative splicing of acetylcholinesterase transcripts in Torpedo electric organ; primary structure of the precursor of the glycolipid-anchored dimeric form.

Abstract

In this paper, we show the existence of alternative splicing in the 3′ region of the coding sequence of Torpedo acetylcholinesterase (AChE). We describe two cDNA structures which both diverge from the previously described coding sequence of the catalytic subunit of asymmetric (A) forms (Schumacher et al., 1986; Sikorav et al., 1987). They both contain a coding sequence followed by a non‐coding sequence and a poly(A) stretch. Both of these structures were shown to exist in poly(A)+ RNAs, by S1 mapping experiments. The divergent region encoded by the first sequence corresponds to the precursor of the globular dimeric form (G2a), since it contains the expected C‐terminal amino acids, Ala‐Cys. These amino acids are followed by a 29 amino acid extension which contains a hydrophobic segment and must be replaced by a glycolipid in the mature protein. Analyses of intact G2a AChE showed that the common domain of the protein contains intersubunit disulphide bonds. The divergent region of the second type of cDNA consists of an adjacent genomic sequence, which is removed as an intron in A and Ga mRNAs, but may encode a distinct, less abundant catalytic subunit. The structures of the cDNA clones indicate that they are derived from minor mRNAs, shorter than the three major transcripts which have been described previously (14.5, 10.5 and 5.5 kb). Oligonucleotide probes specific for the asymmetric and globular terminal regions hybridize with the three major transcripts, indicating that their size is determined by 3′‐untranslated regions which are not related to the differential splicing leading to A and Ga forms.

Association of Bile‐Salt‐Dependent Lipase with Membranes of Human Pancreatic Microsomes

“…Anchoring by a KDEL peptide sequence receptor as described for the liver microsomal carboxylic ester hydrolase 1361 or by a stop-translocation signal 1371 can also be ruled out as no such sequences were present on any BSDL [S, 9, 30, 381. The possible involvement of a (Ose),,GroPIns tail as described for acetylcholinesterase [ 31 ] which is structurally related to BSDL [30] or the association with a (Ose),,GroPlnstailed protein, can also be ruled out. A Golgi retention signal [391 is also not present on any known BSDL sequence 18.…”

Determinants for glycophospholipid anchoring of the Saccharomyces cerevisiae GAS1 protein to the plasma membrane.

“…This was first established for different forms of the variant surface glycoprotein of T. brucei (7,32), the mammalian antigen Thy-1 (60,68), and placental alkaline phosphatase (51,53). To date, processing of the C-terminal hydrophobic domain has been demonstrated for more than a dozen distinct GPI-anchored proteins (15,22,27,29,35,36,47,62,65).…”

“…This particular feature seems to be important in the mechanism of anchor addition. In all cases studied so far, addition of the GPI anchor involves the removal of 17 to 31 residues from the C terminus of a larger precursor (7,15,22,27,29,32,35,36,47,51,53,60,62,65,68). Since processing rapidly follows protein synthesis (2, 18, 24), it is believed that the GPI moiety is preassembled and transferred en bloc to the protein in the endoplasmic reticulum.…”

Synaptic and Epidermal Accumulations of Human Acetylcholinesterase Are Encoded by Alternative 3′-Terminal Exons

“…with noncatalytic subunits, hydrodynamic properties, and sites of subcellular localization (17). One level at which this diversity is controlled appears to be alternative splicing of 3Ј exons (11,15,28). Transfections of AChE-coding sequences into mammalian cells indicated that alternative splicing alone could account for these multiple molecular forms of AChE (5,12,14,16).…”