Tmem30a, also named CDC50A, is the β -subunit of P4 -ATPase. P4 -ATPases function as lipid flippases to maintain the abundance of phosphatidylserine (PS) and phosphatidylethanolamine (PE) in the inner leaflet of the mammalian plasma membrane, and Tmem30a facilitates their transport and functions. Its proper function is crucial for maintaining cellular stability and homeostasis, and its deficiency has wide-ranging impacts on various biological processes [3].

In hair cells of the cochlea, deletion of Tmem30a in mice led to disrupted planar polarity and stereocilia bundles, progressive hair cell loss starting at P7 and finishing around P14, and ultimately auditory dysfunction. This is due to overwhelming endoplasmic reticulum stress caused by excessive ATP8A2 accumulation in the cytoplasm without the Tmem30a chaperone [1].

In podocytes, Tmem30a expression was downregulated in patients with FSGS, adriamycin-induced mice, and podocyte-specific Tmem30a loxP/loxP; NPHS2-Cre mice. Its deficiency was associated with increased pyroptosis-related proteins, suggesting it may protect against podocyte injury by inhibiting pyroptosis [2].

In endothelial cells, knockdown of Tmem30a in primary human retinal endothelial cells reduced tube formation, and EC-specific deletion of Tmem30a in mice led to retarded retinal vascular development, impaired vessel barrier integrity, and reduced EC proliferation by inhibiting VEGF-induced signaling [4].

In retinal rod bipolar cells, RBC-specific Tmem30a knockout mice showed defective RBC function, progressive RBC death, dendritic sprouting, and impaired synaptic efficacy [5].

In B-cell lymphoma, TMEM30A loss-of-function mutations were associated with a favorable outcome, increased accumulation of chemotherapy drugs, and enhanced anti-CD47 blockade effect, while also increasing B-cell signaling following antigen stimulation [6].

In leukemia cells, deletion of Tmem30a led to increased surface levels of phosphatidylserine, reduced NK cell degranulation and cytokine production, and lower susceptibility to NK cell cytotoxicity [7].

In renal tubular epithelial cells, knockdown of Tmem30a reduced vesicle transporter protein synthesis, leading to decreased transport and expression of SGLT2 and reduced glucose absorption [8]. Liver-specific deficiency of Tmem30a developed spontaneous hepatocellular carcinoma [9].

In conclusion, Tmem30a is essential for maintaining cell polarity, membrane homeostasis, and normal physiological functions in multiple cell types. Gene knockout and conditional knockout mouse models have revealed its crucial roles in diseases such as sensorineural hearing loss, podocytopathies, vascular development-related disorders, retinal diseases, lymphoma, leukemia, and hepatocellular carcinoma, providing potential therapeutic targets for these diseases.