A novel clathrin homolog that co-distributes with cytoskeletal components functions in the trans-Golgi network

A clathrin homolog encoded on human chromosome 22 (CHC22) displays distinct biochemistry, distribution and function compared with conventional clathri n heavy chain (CHC17), encoded on chromosome 17, CHC22 protein is upregulat ed during myoblast differentiation into myotubes and is expressed at high l evels in muscle and at low levels in non-muscle cells, relative to CHC17, T he trimeric CHC22 protein does not interact with clathrin heavy chain subun its nor bind significantly to clathrin light chains. CHC22 associates with the AP1 and AP3 adaptor complexes but not with AP2, In non-muscle tells, CH C22 localizes to perinuclear vesicular structures, the majority of which ar e not clathrin coated, Treatments that disrupt the actin-myosin cytoskeleto n or affect sorting in the trans-Golgi network (TGN) cause CHC22 redistribu tion. Overexpression of a subdomain of CHC22 induces altered distribution o f TGN markers. Together these results implicate CHC22 in TGN membrane traff ic involving the cytoskeleton.