Ceroid-lipofuscinosis neuronal proteins (CLN proteins)

Ceroid-lipofuscinosis neuronal (CLN) proteins are a heterogeneous group of at least 13 distinct proteins (CLN1–CLN14) whose mutations lead to Neuronal Ceroid Lipofuscinoses (NCLs), a family of fatal neurodegenerative lysosomal storage disorders collectively known as Batten disease [13, 19]. These proteins are primarily localized to the lysosome, endoplasmic reticulum, or endomembrane system, where they perform essential roles in protein degradation, lipid thioester cleavage, and vesicular trafficking [15, 18]. For instance, CLN1 (PPT1) and CLN2 (TPP1) are soluble lysosomal enzymes, while CLN3 (Battenin) is a transmembrane protein involved in endosomal regulation [3, 4, 5]. Deficiency in any of these proteins results in the toxic accumulation of autofluorescent lipopigments (ceroid and lipofuscin) within neurons, leading to progressive cognitive decline, motor dysfunction, drug-resistant epilepsy, and vision loss [1, 22]. Therapeutic targeting of CLN proteins has seen significant advancement with the approval of cerliponase alfa (Brineura), a recombinant enzyme replacement therapy for CLN2 disease that is delivered directly into the brain to bypass the blood-brain barrier [2, 9]. Other therapeutic avenues under intensive investigation include AAV-mediated gene therapies for CLN1, CLN3, and CLN6, as well as antisense oligonucleotides (ASOs) designed to restore functional protein expression [7, 14, 21]. Small molecule approaches, such as the use of cysteamine for CLN1 or immunosuppressants like mycophenolate mofetil for CLN3, aim to mitigate secondary pathology like neuroinflammation and storage material buildup [6, 10, 11]. Despite these advances, early diagnosis remains critical as current treatments primarily aim to slow disease progression rather than reverse established neurological damage [1, 23].

Other names

Batten disease proteinsNeuronal ceroid lipofuscinosis proteinsNCL proteinsCLN1-CLN14

Enzyme replacement therapy (restoring deficient TPP1 or PPT1 activity), Gene replacement therapy (AAV-mediated delivery of functional genes), Substrate reduction therapy, Autophagy modulation, and Anti-inflammatory action [1, 4, 5, 12, 21].