Peripheral membrane component of the cis-Golgi stack that acts as a membrane skeleton that maintains the structure of the Golgi apparatus, and as a vesicle thether that facilitates vesicle fusion to the Golgi membrane (PubMed:9150144, PubMed:20197635). Required for normal protein transport from the endoplasmic reticulum to the Golgi apparatus and the cell membrane (By similarity). Together with p115/USO1 and STX5, involved in vesicle tethering and fusion at the cis-Golgi membrane to maintain the stacked and inter-connected structure of the Golgi apparatus (PubMed:10679020, PubMed:11035033, PubMed:18167358). Plays a central role in mitotic Golgi disassembly: phosphorylation at Ser-37 by CDK1 at the onset of mitosis inhibits the interaction with p115/USO1, preventing tethering of COPI vesicles and thereby inhibiting transport through the Golgi apparatus during mitosis (PubMed:9753325). Also plays a key role in spindle pole assembly and centrosome organization (PubMed:26165940). Promotes the mitotic spindle pole assembly by activating the spindle assembly factor TPX2 to nucleate microtubules around the Golgi and capture them to couple mitotic membranes to the spindle: upon phosphorylation at the onset of mitosis, GOLGA2 interacts with importin-alpha via the nuclear localization signal region, leading to recruit importin-alpha to the Golgi membranes and liberate the spindle assembly factor TPX2 from importin-alpha. TPX2 then activates AURKA kinase and stimulates local microtubule nucleation. Upon filament assembly, nascent microtubules are further captured by GOLGA2, thus linking Golgi membranes to the spindle (By similarity). Regulates the meiotic spindle pole assembly, probably via the same mechanism (By similarity). Also regulates the centrosome organization (By similarity). Also required for the Golgi ribbon formation and glycosylation of membrane and secretory proteins (By similarity). Homodimer, may assemble into homohexamers (By similarity). Homotetramer; forms a parallel homotetramer with a flexible rod-like structure that can give rise to I- and Y-shaped conformations (PubMed:25787021). Interacts with GORASP1/GRASP65 (PubMed:11739401, PubMed:25787021, PubMed:9346242, PubMed:9628863). The homooligomer forms a complex with GORASP1 with a 1:1 stoichiometry (PubMed:25787021). Interacts with RAB1B that has been activated by GTP-binding (PubMed:18167358). Interacts with p115/USO1; interaction with p115/USO1 inhibits interaction with STX5 and/or RAB1B (PubMed:9150144, PubMed:9753325, PubMed:10744704, PubMed:10769027, PubMed:18167358). Interacts with STX5 (PubMed:18167358). Interacts with ZFPL1 (By similarity). Interacts with AKAP450/AKAP9; leading to recruit AKAP450/AKAP9 to the cis-Golgi (By similarity). Associates with the mitotic spindle during mitosis. Extended rod-like protein with long coiled-coil domains. The nuclear localization signal (cNLS) mediates interaction with importin-alpha, recruiting importin-alpha to the Golgi membrane and liberating TPX2. Phosphorylated at Ser-37 by CDK1 at the onset of mitosis, inhibiting the interaction with p115/USO1 and triggering Golgi disassembly (PubMed:9150144, PubMed:9753325). A report however suggests that Golgi disassembly is independent of phosphorylation at Ser-37 (PubMed:20699666). Phosphorylated at Ser-37 in prophase as the Golgi complex starts to break down, and remains phosphorylated during further breakdown and partitioning of the Golgi fragments in metaphase and anaphase. In telophase, GM130 is dephosphorylated by PP2A as the Golgi fragments start to reassemble (PubMed:10769027). Cleaved by caspases at the onset of apoptosis. Methylation by PRMT5 is required for Golgi ribbon formation. Belongs to the GOLGA2 family. Truncated N-terminus.