Possible role in intracellular signaling and cytoskeleton dynamics at the Golgi. Expressed in kidney, Leydig cells in the testis, epithelial cells in the prostate gland and Langerhans islet in the pancreas. Isoform 1 and isoform 3 are strongly expressed in Purkinje cells and to a lower extent in other neurons (at protein level). Widely expressed at low levels. More strongly expressed in testis and pancreas. Defects in PLEKHG4 were initially thought (PubMed:16001362) to be the cause of spinocerebellar ataxia 16q22-linked. However, it was later shown (PubMed:17611710) that it is not the case. Spinocerebellar ataxia 16q22-linked, also known as spinocerebellar ataxia type 31 (SCA31), is caused by defects in BEAN gene.