Differential distribution of cAMP-dependent protein kinase isoforms in various tissues of the bivalve mollusc Mytilus galloprovincialis.

The cAMP signalling pathway is involved in the regulation of basic physiological processes in bivalve molluscs. We had previously identified and characterized two isoforms of cAMP-dependent protein kinase (PKA) from the sea mussel Mytilus galloprovincialis that differ at their regulatory (R) subunit, namely, R(myt1) or R(myt2). Here we investigated the immunohistochemical expression of both PKA isoforms in various mussel tissues.

Differential distribution of cAMP-dependent protein kinase isoforms in the mantle of the bivalve mollusc Mytilus galloprovincialis.

Two different isoforms of the regulatory (R) subunit of cAMP-dependent protein kinase (PKA), named R(myt1) and R(myt2), had previously been identified in the sea mussel Mytilus galloprovincialis. R(myt1) and R(myt2) were differentially distributed in the various cell types comprising the mussel mantle. R(myt1) was found the only isoform to be present in the auxiliary cells of female follicles and the cubic epithelium of the middle fold of mantle edge.

Identification of multiple isoforms of the cAMP-dependent protein kinase catalytic subunit in the bivalve mollusc Mytilus galloprovincialis.

Several isoforms of the cAMP-dependent protein kinase catalytic subunit (C-subunit) were separated from the posterior adductor muscle and the mantle tissues of the sea mussel Mytilus galloprovincialis by cation exchange chromatography, and identified by: (a) protein kinase activity; (b) antibody recognition; and (c) peptide mass fingerprinting. Some of the isozymes seemed to be tissue-specific, and all them were phosphorylated at serine and threonine residues and showed slight but significant differences in their apparent molecular mass values, which ranged from 41.3 to 44.

CK2-mediated phosphorylation of a type II regulatory subunit of cAMP-dependent protein kinase from the mollusk Mytilus galloprovincialis.

Two isoforms of regulatory (R) subunit of cAMP-dependent protein kinase (PKA), named R(myt1) and R(myt2), were identified so far in the sea mussel Mytilus galloprovincialis. Out of them, only R(myt2) was phosphorylated in vitro by casein kinase 2 (CK2) using GTP as phosphate donor. CK2 catalytic subunit (CK2alpha) itself was sufficient to phosphorylate R(myt2), but phosphorylation was enhanced by the presence of the regulatory subunit CK2beta.

Isoforms of cAMP-dependent protein kinase in the bivalve mollusk Mytilus galloprovincialis: activation by cyclic nucleotides and effect of temperature.

Two different isoforms of cAMP-dependent protein kinase (PKA) have been partially purified from the posterior adductor muscle and the mantle tissue of the sea mussel Mytilus galloprovincialis. The holoenzymes contain as regulatory subunit (R) the previously identified isoforms Rmyt1 and Rmyt2, and were named PKAmyt1 and PKAmyt2, respectively. Both cAMP and cGMP can activate these PKA isoforms completely, although they exhibit a sensitivity approximately 100-fold higher for cAMP than for cGMP.