COG5 is a component of the Conserved Oligomeric Golgi (COG) complex, which facilitates retrograde Golgi trafficking. Disruptions in COG5 can lead to protein misfolding. The COG complex, along with SNARE and Sec1/Munc18 (SM) proteins, is required for vesicle docking and fusion at the Golgi, playing a crucial role in maintaining cellular protein homeostasis [4].

COG5 variants have been associated with multiple disorders. In patients with Leber congenital amaurosis (LCA), COG5 compound-heterozygous variants can result in a complex LCA phenotype with microcephaly and skeletal dysplasia. These variants lead to fragmentation of the Golgi apparatus, upregulation of the UPR modulator PKR-like endoplasmic reticulum kinase (PERK), and induction of DNA damage in cultured cells and murine retina [1]. Mutations in COG5 are also related to a distinct congenital disorder of glycosylation (type IIi), where missense variants can alter protein solubility and stability, disrupt the COG5-COG7 interaction, and lead to a broad clinical spectrum from mild to severe phenotypes [2,3].

In conclusion, COG5 is essential for retrograde Golgi trafficking and maintaining ER protein homeostasis. Studies on COG5-related disorders, including LCA and congenital disorders of glycosylation, highlight its importance in these disease conditions. Understanding the role of COG5 through model-based research, such as in murine retina experiments, provides insights into the underlying molecular mechanisms of these diseases.

References:

1. Tabbarah, Sami, Tavares, Erika, Charish, Jason, Heon, Elise, Monnier, Philippe P. 2020. COG5 variants lead to complex early onset retinal degeneration, upregulation of PERK and DNA damage. In Scientific reports, 10, 21269. doi:10.1038/s41598-020-77394-3. https://pubmed.ncbi.nlm.nih.gov/33277529/

2. Khabou, Boudour, Sahari, Umar Bin Mohamad, Ben Issa, Abir, Reversade, Bruno, Charfi Triki, Chahnez. 2024. Characterization of a missense variant in COG5 in a Tunisian patient with COG5-CDG syndrome and insights into the effect of non-synonymous variants on COG5 protein. In Journal of human genetics, 69, 591-597. doi:10.1038/s10038-024-01273-2. https://pubmed.ncbi.nlm.nih.gov/38987656/

3. Rymen, Daisy, Keldermans, Liesbeth, Race, Valérie, Matthijs, Gert, Jaeken, Jaak. 2012. COG5-CDG: expanding the clinical spectrum. In Orphanet journal of rare diseases, 7, 94. doi:10.1186/1750-1172-7-94. https://pubmed.ncbi.nlm.nih.gov/23228021/

4. Ha, Jun Yong, Pokrovskaya, Irina D, Climer, Leslie K, Lupashin, Vladimir V, Hughson, Frederick M. 2014. Cog5-Cog7 crystal structure reveals interactions essential for the function of a multisubunit tethering complex. In Proceedings of the National Academy of Sciences of the United States of America, 111, 15762-7. doi:10.1073/pnas.1414829111. https://pubmed.ncbi.nlm.nih.gov/25331899/