Protein with tau-like repeats (PTL-1) is the sole MAP2/MAP4/tau homolog in Caenorhabditis elegans (C. elegans). Dysregulation of tau is a pathological hallmark of neurodegenerative diseases such as Alzheimer’s disease. Therefore, reducing tau levels has been suggested as a therapeutic strategy. We used PTL-1 in C. elegans to model the biological functions of a tau-like protein without the complication of functional redundancy. We have shown that PTL-1 maintains the age-related structural integrity of neurons, suggesting that excessive reduction in the levels of a tau-like protein is detrimental. Our data also demonstrates that the regulation of neuronal ageing by PTL-1 occurs via a cell-autonomous mechanism. We transgenically re-expressed PTL-1 in a null mutant background using a pan-neuronal promoter to show that PTL-1 functions in neurons to maintain structural integrity. We next expressed PTL-1 in touch neurons and showed rescue of the neuronal ageing phenotype of ptl-1 mutant animals in these neurons but not in another neuronal subset, the ventral nerve cord GABAergic neurons. Knockdown of PTL-1 specifically in touch neurons also resulted in premature neuronal ageing in these neurons but not in GABAergic neurons, further supporting the conclusion that PTL-1 functions in a cell-autonomous manner. Intriguingly, our data also demonstrates that ptl-1 mutants are short-lived. Expression of PTL-1 in touch neurons alone was unable to rescue the shortened lifespan observed in null mutants, but pan-neuronal re-expression of PTL-1 restored wild-type longevity, indicating that premature neuronal aging and organismal ageing can be decoupled. Overall, our findings suggest that some of the effects of tau pathology may result from the loss of physiological tau function, and not solely from a toxic gain-of-function due to accumulation of tau.