APOL1

APOL1 Full Name

apolipoprotein L, 1

APOL1 Introduction

Apolipoprotein L1 (APOL1) is a secreted lipid-binding protein and integral member of the apolipoprotein family, primarily synthesized in the liver and abundantly incorporated into circulating high-density lipoprotein (HDL) particles in human plasma. Encoded by the APOL1 gene located on human chromosome 22q12.3, this multifunctional protein exhibits unique species-specific expression patterns and serves as a critical regulator of lipid transport, cellular ion homeostasis, innate immune defense, and renal physiological function. Unlike conventional apolipoproteins that solely mediate lipid metabolism, APOL1 possesses distinctive pore-forming activity, enabling it to modulate membrane permeability and cellular stress responses in multiple tissue types. Widely studied in nephrology and immunology, APOL1 not only participates in systemic lipid trafficking and cholesterol homeostasis but also functions as a natural antimicrobial factor against parasitic pathogens. Emerging high-quality research confirms that genetic variants, aberrant expression, and abnormal activation of APOL1 are closely linked to hereditary kidney diseases, cardiovascular disorders, inflammatory injuries, and tumor microenvironment remodeling, making APOL1 a high-priority clinical biomarker and targeted therapeutic gene for human metabolic and renal diseases.

Figure 1. Schematic structure of APOL1.

Pathophysiological and Clinical Significance of APOL1
Genetic variation, overexpression, or abnormal activation of APOL1 is a major genetic driver of human renal diseases and is closely associated with multiple systemic disorders, possessing pivotal clinical diagnostic and prognostic value. The well-characterized G1 and G2 coding variants of APOL1 are prevalent in African ancestry populations and significantly increase the risk of multiple progressive kidney diseases, including focal segmental glomerulosclerosis (FSGS), hypertensive nephropathy, and end-stage renal disease (ESRD). Mutant APOL1 protein induces persistent cytotoxicity, podocyte injury, glomerular sclerosis, and renal tubular inflammation, leading to irreversible renal function decline. Beyond nephropathy, dysregulated APOL1 activity contributes to cardiovascular disease progression by promoting vascular endothelial injury, atherosclerotic plaque formation, and lipid metabolic disorders. Moreover, abnormal APOL1 expression modulates tumor cell survival and inflammatory microenvironment, affecting the progression of multiple solid tumors. Clinically, APOL1 genotyping and protein expression detection have become important auxiliary diagnostic tools for hereditary renal diseases, and targeted inhibition of APOL1 cytotoxic activity represents a promising therapeutic strategy for treating refractory kidney disorders.

Clinical Significance
The APOL1 G1 and G2 risk variants are among the most powerful genetic risk factors for non-diabetic chronic kidney disease known. Individuals carrying two risk alleles (homozygous for G1, homozygous for G2, or compound heterozygous G1/G2) have dramatically increased risk of developing several forms of kidney disease. In focal segmental glomerulosclerosis (FSGS), APOL1 risk variants increase risk by approximately 10- to 17-fold. In HIV-associated nephropathy (HIVAN), the risk increase is approximately 29- to 89-fold. In hypertension-attributed end-stage kidney disease (ESKD), APOL1 risk variants increase risk by approximately 7- to 10-fold. In sickle cell nephropathy, APOL1 risk variants increase risk of proteinuria and kidney function decline. The kidney diseases associated with APOL1 risk variants typically present in adulthood, progress more rapidly, and have a higher rate of progression to ESKD compared to non-APOL1-associated kidney diseases. The penetrance of APOL1-associated kidney disease is incomplete, however, suggesting that additional genetic modifiers or environmental triggers (such as viral infections, interferon exposure, or other stressors) are required for disease manifestation.

Alternate Names for APOL1

APOL1; apolipoprotein L, 1; APOL; APO-L; FSGS4; APOL-I; apolipoprotein L1;