Ras

Ras is a term with multiple uses in science and geography. In biology, Ras refers to a family of small GTPases that regulate cell growth, differentiation, and survival. The human Ras genes include HRAS, KRAS, and NRAS; they function as molecular switches, cycling between active GTP-bound and inactive GDP-bound forms, controlled by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Activated Ras engages downstream signaling pathways such as the MAP kinase/ERK pathway, the PI3K-AKT pathway, and the RalGEF pathway, influencing transcription and metabolism.

Oncogenic mutations in Ras genes were among the first described oncogenes; mutations at codons 12, 13, and 61 decrease intrinsic GTPase activity, locking Ras in an active state and promoting uncontrolled proliferation. Ras mutations are common in several cancers, including pancreatic, colorectal, and lung cancers. Direct pharmacologic targeting of Ras has been historically challenging, but recent inhibitors targeting specific Ras mutants, such as KRAS G12C, show clinical activity. Other approaches include targeting downstream effectors or disrupting Ras's membrane localization via farnesyltransferase inhibitors, though resistance and specificity remain issues.

In geography and linguistics, Ras is a word in Arabic meaning head, tip, or cape, used in many place names to denote coastal promontories or capes, for example Ras al-Khaimah, Ras Tanura, and Ras Ghan. It may also appear as a surname or part of personal names in some cultures. The term is distinct from other uses of "Ras" in technology or culture, which are not implied unless specified.