PROM1

PROM1, also known as prominin-1 and CD133, is a pentaspan transmembrane glycoprotein encoded by the PROM1 gene. It is widely used as a marker to identify adult stem cells and cancer stem cells across multiple tissues, and it has been studied for its roles in development and disease.

The protein contains five transmembrane segments with two large extracellular loops, and the N- and C-termini are oriented toward the cytoplasm. The extracellular regions are glycosylated. PROM1 localizes to the plasma membrane, particularly on microvilli and cilia in various epithelia, and in the retina it is associated with photoreceptor outer segments.

PROM1 is expressed in several stem and progenitor cell populations, including neural, hematopoietic, epithelial, and retinal cells. It is thought to participate in the maintenance of stem cell properties and cell polarity, and it may influence membrane organization and curvature through interactions with cholesterol-rich lipid microdomains. In the retina, prominin-1 is involved in disc morphogenesis and ciliogenesis, contributing to photoreceptor structure and function.

Clinical relevance for PROM1 includes inherited retinal diseases; specific mutations have been linked to cone-rod dystrophy and retinitis pigmentosa-like conditions, leading to vision loss. In oncology, CD133 expression marks subsets of cancer stem cells in a variety of tumors, though its prognostic value is context-dependent. Research use often employs antibodies against PROM1 (for example, AC133) to isolate stem cell–enriched populations.

Genetically, PROM1 is located on chromosome 4 in humans (approximately 4p15.33) and exhibits multiple splice variants. The protein is evolutionarily conserved across vertebrates, reflecting a preserved role in membrane organization, ciliogenesis, and stem cell biology.