Essential signaling protein which has a major role in germline and embryonic development; involved in cell fate decisions that require cell-cell interactions (PubMed:8156602, PubMed:16319922, PubMed:19379690). Probable membrane-bound receptor for putative ligands lag-2 and apx-1 (PubMed:8156602, PubMed:7607081). Upon ligand activation, and releasing from the cell membrane, the glp-1/Notch intracellular domain (NICD) probably forms a transcriptional activator complex with lag-1 and lag-3 and regulates expression of various genes; targets in the germline include lst-1 and sygl-1 (PubMed:9003776, PubMed:10884418, PubMed:16319922, PubMed:32196486, PubMed:16197940, PubMed:7566091, PubMed:19379690). Involved in the specification of the cell fates of the blastomeres, ABa and ABp (PubMed:8156602). Proper signaling by glp-1 induces ABa descendants to produce anterior pharyngeal cells, and ABp descendants to adopt a different fate (PubMed:8156602). Contributes to the establishment of the dorsal-ventral axis in early embryos (PubMed:8156602). Required in postmitotic neurons in order to maintain the developmentally arrested larval state known as dauer, probably in response to lag-2 (PubMed:18599512). Regulates germ cell mitotic proliferation probably by regulating MAP kinase phosphatase lip-1 expression (PubMed:16319922, PubMed:22278922). Required for oocyte growth control (PubMed:19502484). Plays a negative role in lifespan (PubMed:21906946, PubMed:24332851, PubMed:28853436). Interacts with sel-10. When activated, the glp-1/Notch intracellular domain (NICD) may become a component of a complex consisting of at least the NICD, lag-1 and lag-3. Localized to axons during dauer larval stage. The glp-1/Notch intracellular domain (NICD) may become localized to the nucleus after ligand activation. Expressed in the distal mitotic region of the germ line (PubMed:7607081). May be absent from the gonadal distal tip cell (DTC) (PubMed:7607081). Acts on ABp development during 4-cell and 12-cell stages, and on ABa development during 12-cell and 28-cell stages (PubMed:8156602). Expressed in various neurons, including AWC, during the dauer larval stage (PubMed:18599512). Upon binding its ligands, it is cleaved (S2 cleavage) in its extracellular domain, close to the transmembrane domain (By similarity). S2 cleavage is probably mediated by the metalloproteases adm-4 and sup-17 (PubMed:16197940). It is then cleaved (S3 cleavage) downstream of its transmembrane domain, releasing it from the cell membrane; S3 cleavage requires a multiprotein gamma-secretase complex, which may include presenilin sel-12 (PubMed:7566091). RNAi-mediated knockdown causes an increase in lifespan and a moderate increase in aak-2 phosphorylation (PubMed:24332851). RNAi-mediated knockdown in a rsks-1 mutant background reduces the formation of proximal germ cell tumors (PubMed:22278922). RNAi-mediated knockdown results in abnormally large oocytes (PubMed:19502484).