alpha-actinin in different invertebrate muscle cell types of Drosophila melanogaster, the earthworm Eisenia foetida, and the snail Helix aspersa

The presence and distribution of alpha-actinin has been studied in several invertebrate muscle cell types. These comprised transversely striated muscl e (flight muscle) from the fruit fly Drosophila melanogaster, transversely striated muscle (heart muscle) from the snail Helix aspersa, obliquely stri ated muscle (body wall muscle) from the earthworm Eisenia foetida, smooth m uscle (retractor muscle) from H, aspersa, and smooth muscle (outer muscular layer of the pseudoheart) from E. foetida. The study was carried by means of Western blot analysis, ELISA, and immunohistochemical electron microscop y, using anti alpha-actinin antibody. Immunoreaction for a protein with the same molecular weight as that of mammalian alpha-actinin was detected in a ll muscle types studied, although the amount and intensity of immunoreactio n varied among them. In the insect muscle, immunolabelling was found along the whole Z-line. Ln both the transversely striated muscle from the snail a nd the obliquely striated muscle from the earthworm, immunolabelling did no t occupy the whole Z-line but showed discontinuous, orderly arranged patche s along the Z-line course. In the two smooth muscles studied (snail and ear thworm), immunolabelling was limited to small patches which did not show an apparently ordered distribution. Since it is assumed that a-actinin is loc ated at the anchorage sites for actin filaments, present observations sugge st that, only in the Drosophila muscle, actin filaments are parallely arran ged in all their course, whereas in the other invertebrate muscles studied these filaments converge on discontinuously distributed anchorage sites.