Protein with pleiotropic attributes mediated in a cell-compartment- and tissue-specific manner, which include the plasma membrane-associated cell signaling functions, mitochondrial chaperone, and transcriptional co-regulator of transcription factors in the nucleus (By similarity). Plays a role in adipose tissue and glucose homeostasis in a sex-specific manner (By similarity). Contributes to pulmonary vascular remodeling by accelerating proliferation of pulmonary arterial smooth muscle cells (By similarity). In the mitochondria, together with PHB2, forms large ring complexes (prohibitin complexes) in the inner mitochondrial membrane (IMM) and functions as chaperone protein that stabilizes mitochondrial respiratory enzymes and maintains mitochondrial integrity in the IMM, which is required for mitochondrial morphogenesis, neuronal survival, and normal lifespan (By similarity). The prohibitin complex, with DNAJC19, regulates cardiolipin remodeling and the protein turnover of OMA1 in a cardiolipin-binding manner (By similarity). Regulates mitochondrial respiration activity playing a role in cellular aging. The prohibitin complex plays a role of mitophagy receptor involved in targeting mitochondria for autophagic degradation. Involved in mitochondrial-mediated antiviral innate immunity, activates DDX58/RIG-I-mediated signal transduction and production of IFNB1 and proinflammatory cytokine IL6 (By similarity). In the nucleus, acts as a transcription coregulator, enhances promoter binding by TP53, a transcription factor it activates, but reduces the promoter binding by E2F1, a transcription factor it represses. Interacts with STAT3 to affect IL17 secretion in T-helper Th17 cells. In the plasma membrane, cooperates with CD86 to mediate CD86-signaling in B lymphocytes that regulates the level of IgG1 produced through the activation of distal signaling intermediates. Upon CD40 engagement, required to activate NF-kappa-B signaling pathway via phospholipase C and protein kinase C activation. The mitochondrial prohibitin complex consists of two subunits (PHB1 and PHB2), assembled into a membrane-associated ring-shaped supercomplex of approximately 1 mDa. Interacts with STOML2. Interacts with MAP1LC3B (membrane-bound form LC3-II); the interaction requires PHB2 and takes place upon Parkin-mediated mitochondrial damage. Interacts with STAT3 (unphosphorylated or phosphorylated at 'Ser-727'). Interacts with CLPB (By similarity). Interacts with CD86 (via cytoplasmic domain); the interactions increases after priming with CD40 (By similarity). Belongs to the prohibitin family.