Cbl, short for Casitas B lineage lymphoma, is a multifunctional protein with ubiquitin E3 ligase activity. It plays key roles in various cell pathways, such as those related to cancer onset and progression, hematopoietic development, T cell receptor regulation, and muscle atrophy regulation [2,4,1]. There are three members in the Cbl family: c-Cbl, Cbl-b, and Cbl-c [4]. Cbl proteins can regulate signal transduction and activate receptor tyrosine kinases through tyrosine-kinase-dependent pathways [4].

Cbl-b, for example, is associated with muscle atrophy. It ubiquitinates and induces the degradation of IRS-1, a key intermediate in the IGF-1 signaling, which is involved in unloading muscle atrophy in spaceflight and bedridden patients. A pentapeptide (DGpYMP) can inhibit Cbl-b-mediated IRS-1 ubiquitination, suggesting potential therapeutic approaches for muscle atrophy [1]. In the context of cancer, somatic Cbl mutations have been reported in multiple malignancies, and germline Cbl mutations configure the so-called CBL syndrome, a cancer-predisposing condition with multisystemic involvement [2]. C-Cbl has also been implicated in angiogenesis and human solid organ tumors, highlighting its role in tumorigenesis [3].

In conclusion, Cbl is a crucial regulator in multiple biological processes and disease conditions. The study of Cbl, especially through functional studies in relevant models, has provided insights into its roles in cancer, muscle atrophy, and other diseases, offering potential therapeutic targets for these conditions.