Involved in the assembly of dense bodies and M lines during body wall muscle development. Acts by recruiting downstream of integrin-associated protein pat-6/actopaxin several dense bodies and M line components including unc-89, lim-9, scpl-1 and unc-96 to integrin-mediated attachment sites. May interact (via VWFA domain) with unc-89 (via Ig-like C2-type 1-3) and unc-96 (via C-terminus); cpna-1 binding sites for unc-89 and unc-96 are different. May interact with pat-6. May interact with lim-9 (via LIM domains) and with scpl-1 (via FCP1 homology domain). Colocalizes with unc-89, unc-112, pat-3 and pat-6 at the M-line and with alpha-actinin, unc-112, pat-3 and pat-6 in dense bodies. In body wall muscle cells, colocalizes with beta-integrin pat-3 at integrin adhesion sites. Expressed in body wall muscles (at protein level). Expressed in embryos and in adults. Embryos stop elongation at the 2-fold stage and have defects in the organization of the myofibril lattice. pat-3, deb-1, pat-4 and pat-6 are slightly mislocalized in the post 1.5-fold stage. At the 1.5-fold stage, unc-89 and myo-3 localization is normal. However, at the 1.75- and 2-fold stages, unc-89 and myo-3 are mislocalized into large foci within muscle cells. Belongs to the copine family.