GM130 Is Required for Compartmental Organization of Dendritic Golgi Outposts

Abstract

SUMMARY Golgi complexes (Golgi) play important roles in the development and function of neurons [1–3]. Not only are Golgi present in the neuronal soma (somal Golgi) but they also exist in the dendrites as Golgi outposts [4–7]. Previous studies have shown that Golgi outposts serve as local microtubule organizing centers [8] and secretory stations in dendrites [6, 9]. It is unknown whether the structure and function of Golgi outposts differ from those of somal Golgi. Here we show in Drosophila that, unlike somal Golgi, the biochemically distinct cis, medial, and trans compartments of Golgi are often disconnected in dendrites in vivo. The Golgi structural protein GM130 is responsible for connecting distinct Golgi compartments in soma and dendritic branch points, and specific distribution of GM130 determines the compartmental organization of dendritic Golgi in dendritic shafts. We further show that compartmental organization regulates the role of Golgi in acentrosomal microtubule growth in dendrites and in dendritic branching. Our study provides insights into the structure and function of dendritic Golgi outposts as well as the regulation of compartmental organization of Golgi in general.

Microtubule nucleation and organization in dendrites

“…In class III sensory neurons, outposts exist in both single-and multi-compartment forms. 57 In class I neurons, however, although the Golgi structural protein GM130 is present in the dendrites, 79 only medial-Golgi markers were detected. 20,55 The transcription factor Dar1 is required to create complex dendrite arbor structures.…”

“…Further experiments are required to clarify the relationship between outpost polarity and microtubule nucleation polarity. Because the organization of dendrite Golgi outposts differs from somatic Golgi, 57 especially for single-compartment outposts, it is possible that microtubule nucleation might be able to initiate on either surface of the outpost (and continue solely from that surface).…”

“…In dendrites the biochemically distinct medial and trans compartments, which are characteristically combined into a stack in the soma, are often disconnected into single-compartment Golgi outposts. 57 Single-compartment Golgi outposts can nucleate microtubules, but fusion into a multi-compartment structure within dendrites increases outpost microtubule nucleation activity. 57 The Golgi structural protein GM130 localizes to outposts and promotes the fusion of single-compartment outposts into a multi-compartment structure.…”

“…57 Single-compartment Golgi outposts can nucleate microtubules, but fusion into a multi-compartment structure within dendrites increases outpost microtubule nucleation activity. 57 The Golgi structural protein GM130 localizes to outposts and promotes the fusion of single-compartment outposts into a multi-compartment structure. 57 In addition to this outpost fusion function, GM130 may also recruit AKAP450/Plp to outposts, as it has been shown to link AKAP450/Plp to somatic Golgi for microtubule nucleation.…”

“…57 The Golgi structural protein GM130 localizes to outposts and promotes the fusion of single-compartment outposts into a multi-compartment structure. 57 In addition to this outpost fusion function, GM130 may also recruit AKAP450/Plp to outposts, as it has been shown to link AKAP450/Plp to somatic Golgi for microtubule nucleation. 58 The role of alternative nucleation sites in orienting microtubule nucleation in the dendrite…”