Figure 1. Proteostasis (protein homeostasis). Proteins in a cell are constantly undergoing renewal, as proteins are degraded and synthesized anew. As proteins are synthesized, they must fold properly to acquire their native, functional form (pathway 1). When this protein folding process misfunctions, misfolded proteins arise (pathway 2). Misfolded proteins may either eventually be converted into properly folded proteins (pathway 3) or be degraded (pathway 4). Native, functional proteins can either spontaneously misfold or undergo degradation (unlabeled pathways).